Explanation:
This turned out to be a silly mistake on my part!
There is an Optional mod in FPA+ called "No Door Animations". This was made a very long time ago in FPA+'s development, before
Juiced Patch was a thing. After Juiced Patch released,
I suggested implementing "No Door Animations" via Juiced Patch, so it can be easily applied on top of any other animations mod (not just FPA+). The guys at
Kobraworks added it in as "FastDoors". So I started using it and forgot about it. While wrapping up development of FPA+, I made use of GFL_Life.xtbl to correct some male NPC animations. In doing so, I added one more animation than the game's memory can handle, but my game didn't crash because having "FastDoors" enabled in Juiced Patch made room for that one extra animation by disabling the door animations.
So in the most roundabout way possible, I shot myself in the foot!
Sorry to anyone who experienced this issue. It's entirely my bad. FPA+ should now work fine with or without "FastDoors".
Thanks to
@twintribes and
@Cheezit for raising this issue.