We have been experiencing an annoying FM (bug?). Whenever we change a permission on a given password, FM changes (randomly) permissions for other passwords. It will make some fields unviewable, others unalterable. Similarly, when we add new fields to a protected file, FM assumes we want the highest security possible on those fields, and we have to go in and manually make them available to all.

Is this supposed to happen?

FM will never do that just because

You have probably some mix-up with other passwords through groups, fields, layouts etc.

FM did not do this in 3.x and 4.x. Once 5.x came along, it started. Same passwords, same permissions, same groups. In the fifteen years I've been creating solutions in FM, I have found that FM does do things just because...

Actually, I've had the same problem. I could never identify a pattern, but I know it was doing something it shouldn't have been. I haven't seen it pop up in a while though, as I haven't been altering too many things at that root level.