Error while running event Subsurface::on_object_destroyed (ID 178)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__Subsurface/control.lua:809: in function <Subsurface/control.lua:800>

This happens when I try to use cave sealant on an entrance. When I use it from the surface it doesn't crash but it still appears bugged. I can no longer use the entrance and it loses a wire connection but the entity is still there visually and it blocks my path.

On further testing, it only happens if the entrance is clear of any walls. I could safely seal one by building the walls into it. By the way, how does this mod handle modded planets and resources? It seems fine with rabbasca and Nauvis underground, but it crashes with Vulcanus underground.

Did you seal the upper or the lower part of the entrance?
There is no special handling of modded planets. Modded resources spawn udnerground if they are spawning overground.
Is it the same error message for volcanus? Could you send a savegame right before you seal the entrance that produces the error? (Please with only relevant mods)