Honestly, I keep forgetting the errorlog exists. In it, I found this:
undefined local plant material set to default: ROOT_MUCK SEED
undefined local plant material set to default: TUBER_BLOATED SEED
*** Error(s) finalizing the creature FLESH_BALL
undefined local creature material set to default: FLESH_BALL MUSCLE
*** Error(s) finalizing the creature POND_GRABBER
undefined local creature material set to default: POND_GRABBER CLAW
*** Error(s) finalizing the creature CAVE_FLOATER
undefined local creature material set to default: CAVE_FLOATER LEATHER
*** Error(s) finalizing the creature CAVE_BLOB
undefined local creature material set to default: CAVE_BLOB LEATHER
*** Error(s) finalizing the creature WAMBLER_FLUFFY
undefined local creature material set to default: WAMBLER_FLUFFY TALLOW
undefined local creature material set to default: WAMBLER_FLUFFY LEATHER
undefined local creature material set to default: WAMBLER_FLUFFY FAT
undefined local creature material set to default: WAMBLER_FLUFFY HAIR
*** Error(s) finalizing the creature MUSSEL
undefined local creature material set to default: MUSSEL TALLOW
undefined local creature material set to default: MUSSEL LEATHER
*** Error(s) finalizing the creature OYSTER
undefined local creature material set to default: OYSTER TALLOW
undefined local creature material set to default: OYSTER LEATHER
*** Error(s) finalizing the creature PANGOLIN
undefined local creature material set to default: PANGOLIN SKIN
*** Error(s) finalizing the creature PANGOLIN_MAN
undefined local creature material set to default: PANGOLIN_MAN SKIN
*** Error(s) finalizing the creature GIANT_PANGOLIN
undefined local creature material set to default: GIANT_PANGOLIN SKIN
*** Error(s) found in the file "data/save/region1/raw/objects/creature_riverlakepool_new.txt"
BEAVER:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
BEAVER_MAN:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
GIANT_BEAVER:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
*** Error(s) found in the file "data/save/region1/raw/objects/creature_standard.txt"
AQUILOUP:Unrecognized Creature Caste Body Gloss Token: TALON
AQUILOUP:Attack SCRATCH seems to have correct format but could not find proper BPs in any caste, so not added
undefined local plant material set to default: ROOT_MUCK SEED
undefined local plant material set to default: TUBER_BLOATED SEED
*** Error(s) finalizing the creature FLESH_BALL
undefined local creature material set to default: FLESH_BALL MUSCLE
*** Error(s) finalizing the creature POND_GRABBER
undefined local creature material set to default: POND_GRABBER CLAW
*** Error(s) finalizing the creature CAVE_FLOATER
undefined local creature material set to default: CAVE_FLOATER LEATHER
*** Error(s) finalizing the creature CAVE_BLOB
undefined local creature material set to default: CAVE_BLOB LEATHER
*** Error(s) finalizing the creature WAMBLER_FLUFFY
undefined local creature material set to default: WAMBLER_FLUFFY TALLOW
undefined local creature material set to default: WAMBLER_FLUFFY LEATHER
undefined local creature material set to default: WAMBLER_FLUFFY FAT
undefined local creature material set to default: WAMBLER_FLUFFY HAIR
*** Error(s) finalizing the creature MUSSEL
undefined local creature material set to default: MUSSEL TALLOW
undefined local creature material set to default: MUSSEL LEATHER
*** Error(s) finalizing the creature OYSTER
undefined local creature material set to default: OYSTER TALLOW
undefined local creature material set to default: OYSTER LEATHER
*** Error(s) finalizing the creature AQUILOUP
undefined local creature material set to default: AQUILOUP NAIL
undefined local creature material set to default: AQUILOUP FEATHER
*** Error(s) finalizing the creature FAIRY_DRAGON
undefined local creature material set to default: FAIRY_DRAGON CHITIN
*** Error(s) finalizing the creature PANGOLIN
undefined local creature material set to default: PANGOLIN SKIN
*** Error(s) finalizing the creature PANGOLIN_MAN
undefined local creature material set to default: PANGOLIN_MAN SKIN
*** Error(s) finalizing the creature GIANT_PANGOLIN
undefined local creature material set to default: GIANT_PANGOLIN SKIN
*** Error(s) found in the file "data/save/region1/raw/objects/creature_riverlakepool_new.txt"
BEAVER:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
BEAVER_MAN:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
GIANT_BEAVER:Unrecognized Creature Token: ANY_TEMPERATE_SWAMP
*** Error(s) found in the file "data/save/region1/raw/objects/creature_standard.txt"
AQUILOUP:Unrecognized Creature Caste Body Gloss Token: TALON
AQUILOUP:Attack SCRATCH seems to have correct format but could not find proper BPs in any caste, so not added
undefined local plant material set to default: ROOT_MUCK SEED
undefined local plant material set to default: TUBER_BLOATED SEED
*** Error(s) finalizing the creature FLESH_BALL
undefined local creature material set to default: FLESH_BALL MUSCLE
*** Error(s) finalizing the creature POND_GRABBER
undefined local creature material set to default: POND_GRABBER CLAW
*** Error(s) finalizing the creature CAVE_FLOATER
undefined local creature material set to default: CAVE_FLOATER LEATHER
*** Error(s) finalizing the creature CAVE_BLOB
undefined local creature material set to default: CAVE_BLOB LEATHER
*** Error(s) finalizing the creature WAMBLER_FLUFFY
undefined local creature material set to default: WAMBLER_FLUFFY TALLOW
undefined local creature material set to default: WAMBLER_FLUFFY LEATHER
undefined local creature material set to default: WAMBLER_FLUFFY FAT
undefined local creature material set to default: WAMBLER_FLUFFY HAIR
*** Error(s) finalizing the creature MUSSEL
undefined local creature material set to default: MUSSEL TALLOW
undefined local creature material set to default: MUSSEL LEATHER
*** Error(s) finalizing the creature OYSTER
undefined local creature material set to default: OYSTER TALLOW
undefined local creature material set to default: OYSTER LEATHER
*** Error(s) finalizing the creature AQUILOUP
undefined local creature material set to default: AQUILOUP NAIL
undefined local creature material set to default: AQUILOUP FEATHER
*** Error(s) finalizing the creature FAIRY_DRAGON
undefined local creature material set to default: FAIRY_DRAGON CHITIN
*** Error(s) finalizing the creature PANGOLIN
undefined local creature material set to default: PANGOLIN SKIN
*** Error(s) finalizing the creature PANGOLIN_MAN
undefined local creature material set to default: PANGOLIN_MAN SKIN
*** Error(s) finalizing the creature GIANT_PANGOLIN
undefined local creature material set to default: GIANT_PANGOLIN SKIN
*** Error(s) found in the file "data/save/region3/raw/objects/creature_standard.txt"
AQUILOUP:Unrecognized Creature Caste Body Gloss Token: TALON
AQUILOUP:Attack SCRATCH seems to have correct format but could not find proper BPs in any caste, so not added
*** Error(s) found in the file "data/save/region3/raw/objects/creature_tropical_new.txt"
BONGO:Attack HGORE seems to have correct format but could not find proper BPs in any caste, so not added
BONGO:Unrecognized Creature Token: [SET_TL_GROUP
BONGO Color Mod Ending With (CHESTNUT,1) Was Not Used
undefined local plant material set to default: ROOT_MUCK SEED
undefined local plant material set to default: TUBER_BLOATED SEED
*** Error(s) finalizing the creature FLESH_BALL
undefined local creature material set to default: FLESH_BALL MUSCLE
*** Error(s) finalizing the creature POND_GRABBER
undefined local creature material set to default: POND_GRABBER CLAW
*** Error(s) finalizing the creature CAVE_FLOATER
undefined local creature material set to default: CAVE_FLOATER LEATHER
*** Error(s) finalizing the creature CAVE_BLOB
undefined local creature material set to default: CAVE_BLOB LEATHER
*** Error(s) finalizing the creature WAMBLER_FLUFFY
undefined local creature material set to default: WAMBLER_FLUFFY TALLOW
undefined local creature material set to default: WAMBLER_FLUFFY LEATHER
undefined local creature material set to default: WAMBLER_FLUFFY FAT
undefined local creature material set to default: WAMBLER_FLUFFY HAIR
*** Error(s) finalizing the creature MUSSEL
undefined local creature material set to default: MUSSEL TALLOW
undefined local creature material set to default: MUSSEL LEATHER
*** Error(s) finalizing the creature OYSTER
undefined local creature material set to default: OYSTER TALLOW
undefined local creature material set to default: OYSTER LEATHER
*** Error(s) finalizing the creature AQUILOUP
undefined local creature material set to default: AQUILOUP NAIL
undefined local creature material set to default: AQUILOUP FEATHER
*** Error(s) finalizing the creature FAIRY_DRAGON
undefined local creature material set to default: FAIRY_DRAGON CHITIN
*** Error(s) finalizing the creature PANGOLIN
undefined local creature material set to default: PANGOLIN SKIN
*** Error(s) finalizing the creature PANGOLIN_MAN
undefined local creature material set to default: PANGOLIN_MAN SKIN
*** Error(s) finalizing the creature GIANT_PANGOLIN
undefined local creature material set to default: GIANT_PANGOLIN SKIN
*** Error(s) found in the file "raw/objects/creature_standard.txt"
AQUILOUP:Unrecognized Creature Caste Body Gloss Token: TALON
AQUILOUP:Attack SCRATCH seems to have correct format but could not find proper BPs in any caste, so not added
*** Error(s) found in the file "raw/objects/creature_tropical_new.txt"
BONGO:Attack HGORE seems to have correct format but could not find proper BPs in any caste, so not added
BONGO:Unrecognized Creature Token: [SET_TL_GROUP
BONGO Color Mod Ending With (STRIPES_CHESTNUT_WHITE,1) Was Not Used
undefined local plant material set to default: ROOT_MUCK SEED
undefined local plant material set to default: TUBER_BLOATED SEED
*** Error(s) finalizing the creature FLESH_BALL
undefined local creature material set to default: FLESH_BALL MUSCLE
*** Error(s) finalizing the creature POND_GRABBER
undefined local creature material set to default: POND_GRABBER CLAW
*** Error(s) finalizing the creature CAVE_FLOATER
undefined local creature material set to default: CAVE_FLOATER LEATHER
*** Error(s) finalizing the creature CAVE_BLOB
undefined local creature material set to default: CAVE_BLOB LEATHER
*** Error(s) finalizing the creature WAMBLER_FLUFFY
undefined local creature material set to default: WAMBLER_FLUFFY TALLOW
undefined local creature material set to default: WAMBLER_FLUFFY LEATHER
undefined local creature material set to default: WAMBLER_FLUFFY FAT
undefined local creature material set to default: WAMBLER_FLUFFY HAIR
*** Error(s) finalizing the creature MUSSEL
undefined local creature material set to default: MUSSEL TALLOW
undefined local creature material set to default: MUSSEL LEATHER
*** Error(s) finalizing the creature OYSTER
undefined local creature material set to default: OYSTER TALLOW
undefined local creature material set to default: OYSTER LEATHER
*** Error(s) finalizing the creature AQUILOUP
undefined local creature material set to default: AQUILOUP NAIL
undefined local creature material set to default: AQUILOUP FEATHER
*** Error(s) finalizing the creature FAIRY_DRAGON
undefined local creature material set to default: FAIRY_DRAGON CHITIN
*** Error(s) finalizing the creature PANGOLIN
undefined local creature material set to default: PANGOLIN SKIN
*** Error(s) finalizing the creature PANGOLIN_MAN
undefined local creature material set to default: PANGOLIN_MAN SKIN
*** Error(s) finalizing the creature GIANT_PANGOLIN
undefined local creature material set to default: GIANT_PANGOLIN SKIN
And honestly I'm not sure what to do about those. I know that I added the temperate swamp biome to the beavers, because lake and river creatures for some reason only ever spawn once, at first embark. Copy/paste fresh raws from the wiki for the ?
Speaking of copying/pasting raws, copying the raws from my 40.19 version seems to have fixed it for now. Are there any significant differences over the versions?
Considering that MacNewbie could open it just fine, it makes me think the problem is in the installation.