Custom order lost in manage database

Three times in the last week or so I have gone into Manage Database to look at the fields for a table in custom order and found that my previous (non-alphabetical) ordering had been replaced by an alphabetical one. The loss of order also appears to have occurred while I was in the middle of a Manage Database session. I had to reconstruct my previous order to untangle the relationships graph. I have no idea what might have triggered the re-ordering. I checked for file consistency in Recover and discovered no issues. Might my file have nevertheless been corrupted in some way? This behaviour has never occurred prior to these three instances. The idea of going back to an earlier version and reconstructing all of my changes over the last week or two is daunting. Any insight into this strange behaviour would be much appreciated.