Strange issue reported - MySQL with Java front-end app - fields resetting

I have a client with a MySQL based database system and a Java front-end app (which we are currently rebuilding using PHP as Java/Tomcat is way too much overhead for what they need and PHP is much more able to handle these tasks than it was when the Java iteration of this app was built about 8+ years ago.

What was just reported to me is that they are updating their Jobs and setting a ship date (date field in DB) and marking the job as Invoiced (TINYINT with value of 4 in DB) using their front end app. Apparently recently they have been finding that a few days later, the job is no longer marked invoiced, or the ship date has cleared, or both.

I have asked them to start logging what jobs they update and when, then note when they discover one that has reset in hopes of finding some sort of pattern to when these issues occur.

Has anyone ever encountered this, or have some suggestions for things to take a look into? Nothing has changed with their application or the server it is running on, the new rewrite is being done completely separate of any of their hardware.

Thanks for any insight anyone can offer.

Greg