Is anyone else having trouble with the Central File locking users out?

We have a 90 MB project with linked structural file, and anywhere from 3 to 7 users working on local files. Every 2 days they all get locked out because the central file thinks it's busy. The only way to clear the problem has been to make one of the locals into a new Central.

This has happened to other 2010 projects, but much less often.

All users are patched up to the current build.