Threads getting perm deleted when they shouldn't be

[mme42]

We seem to be having a problem with threads getting permanently removed when they shouldn't be. We have permissions set so that only admins can perm delete. Yet, we're seeing "Thread Removed" in the moderator logs for many of the mods (about 1/3 to 1/2 of them). It should be only a soft delete, but it seems they are somehow getting permanently deleted.

I've double checked the permissions for these mods and they shouldn't be able to perm delete. I've tried to replicate the problem on an offline test forum with these mods' accounts but nothing seems to work. The option to perm delete isn't available when using their accounts to delete. It would seem that either there is some kind of bug that is turning a soft delete into a perm delete, or they are finding someway around not being allowed to perm delete. Either way, I can't reproduce it.

Does anybody have any idea what could cause this? It's starting to drive me nuts, haha.

Thanks.