Sounds like it could be a client caching issue.
1. Have the user close the client.
2. Purge the personalization from another machine.
3. Reopen the client and select clear client cache before you open any forms.
If the problem persists, you can also close the client and delete the cache directory manually (C:\ProgramData\Epicor\[appserver-808]). There are also some settings buried in a user.config file under C:\Users\[username]\AppData\local\Epicor\ which you could look at and delete if needed as well but I have never seen them create an issue on a customization.
HTH,
Tanner