Bridge Random "Unstacking" of Thumbnails

Hi there;

I have been experiencing a recurring problem with Bridge.  It seems that everytime I "stack" thumbnails from a completed project, Bridge randomly "unstacks" them.  This is VERY frustrating when you have thousands of images to work with.  I've noticed other users have been experiencing the same issue.  Any suggestions/fixes?   

Thank you.

[Note: I'm a moderator, and I removed your email from this message. Unfortunately, there are both good and bad people in these forums and the good folks have to be careful of the bad folks. I'm sorry about this.]