What is the AI!.BSA file. What does it do? What should it contain?

Mine gets altered regularly and only contains the letter "a". It is a 1 KB file

It's the Archive Invalidation from FOMM. It's supposed to be like that.

Okay, that explains it. Thanks.

I'll see if I can get some support in the FOMM thread. There has been no help on the Nexus forum for some time.

I'm having some texture issues with characters bodies missing. Most issues were cleared up by checking and unchecking the Archive Invalidation option in the Tools Menu—but not all.