We're struggling to get through a FB without crashing. I don't know what 50.09 changed, but it's been rather crash prone whenever we're visited by FBs or invaders. Strangely, no issue with killing other beasts.
'Tis a shame. We've just dug out the bare minimum of the main base at the third cavern, and flooded the farm and cistern.
EDIT: I think it might be related to burrows. Burrow was on, a monster slayer was duking it out on the other side of the raised bridge, and the game was crashing every time regardless of whether the monster slayer lived or not. Turn off the burrow, and suddenly the game doesn't crash. It's reproducible on my save.
Kinda sucks, though. I need my burrows!
EDIT2: Had a thought, though it didn't pan out. I noticed if I unassigned everyone from the burrow, then there would still be a non-zero number of "assigned" dwarves—corrupted with dead dwarves most likely. Maybe deleting and redoing the burrow, then reassigning dwarves would stop the crashes, but no.
Doubt it's the dead dwarves, though. Regardless if you unassign as many as you can, deactivate the burrow, delete the burrow, recreate the burrow, reassign to the burrow, then reactivate the burrow; the game still crashes. Even if the dead dwarves died during an active burrow, I don't see how they can cause a crash without constantly crashing even after the invaders and forgotten beasts are dealt with. Either the "assigned" and "active burrow" states remain and the game should constantly crash, or they don't and there should be a conceivable path to remove the crashing during gameplay; but neither are happening.