Thank you for your post, and thank you for filling out the template. These are common questions we ask.
Unfortunately, we still need some additional information....
Does this always happen? If not, how many times has this happened?
Is it always the same client?
Is it always the same database?
Is there any information in the Event.log file (Library -> FileMaker Server) that is noteworthy?
Any additional information you can provide would be helpful.