The GET_MATERIAL_FROM_REAGENT:peat:PEATFUEL_MAT becomes INORGANIC:PEAT_BRICKS by reference, and that material does not exist. So in effect you have
[REACTION:MAKE_PEAT_BRICKS]
[NAME:make peat bricks]
[BUILDING:SCREW_PRESS:CUSTOM_B]
[REAGENT:peat:1:BOULDER:NONE:NONE:NONE]
[HAS_MATERIAL_REACTION_PRODUCT:PEATFUEL_MAT]
[PRODUCT:100:1:BLOCKS:NONE:nonexistent_material]
[SKILL:PRESSER]
and the game seems to be helpfully suggesting magma as a replacement.
Ahh. So PEATFUEL_MAT isn't a thing, ergo, it defaults to magma.
For clay reactions, there's this line:
[PRODUCT:100:1:CRAFTS:NONE:GET_MATERIAL_FROM_REAGENT:clay:FIRED_MAT]
However, I don't see a definition for what a FIRED_MAT is within the raws, though it's tagged onto clay soils, kaolinite, and all of the clay reactions.
Is it possible to add Inorganic tags like that?
What solution would you suggest?