Mailboxes being "lost"

I have a gpl box that is loosing mailboxes. What happens is the users can no longer receive mail and all of their folders are gone in imap and usermin. If we log into the admin interface and simply bring up the affected account and then hit save everything is back. this is increasing in frequency and also involving more accounts. I can't find anything in the logs i'm open to pointers of where to look.

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Did the mailbox's password perhaps get changed externally, causing IMAP logins to fail? That could explain the behavior you are seeing ..

nopers. i've checked and nothing has changed. The first time i saw this i had to restart dovecot. I can't find anything in the logs this time to explain it.

I wonder if i found it I have another person with limited admin. he created about 15 mail accounts with local delivery and forwarding to at least two other external mailboxes. I've rectified that..and will observe to see if that fixes the issue.

Ok, let us know ..