Regardless of their open/closed state, monsters walk right through Big Doors. They do not have this problem with other doors in my pack (vanilla, natura, carpenter's blocks, Malisis' Doors, etc.) Any ideas?

Version? I've not seen a problem with monsters walking through doors, but certain entities like arrows are an issue. Check Malisis' carriage doors for comparison, as that is what they are based off of.

Version BigDoors-1.7.10-1.1.0.jar. Apologies, I should have mentioned this is 1.7.10. The Carriage Doors also do not stop monsters...they walk right through.

@jaquadro has there been any research into resolving this problem with Big doors. I can confirm that certain entities are not stopped by the doors. (mostly projectile weapons). Mobs are NOT able to walk through the door, BUT they can still see and detect the player as if the door was not there.

I know this is a 1.7.10 issue. A patch to fix would be deeply appreciated.

I have not encountered this issue with the 1.10.2 version.