rharv, sorry I did not respond on the File open backup... I DID try that as soon as you posted it. I have 5 backups and opened all 5. They all are missing the RT 1/2 of the drum track. I was working most of the day on this and saved well over a dozen times in 4 hours or so. So I think each save eliminates a prior backup, retaining only the most recent 5 saves.

My fix for this particular tune was to merge the 1/2 drum track to a mono track. Sound is not quite the same, but at least I have all my edits ie, moving fills around, adjusting gain on certain sections.... deleting playing during held chords etc.

Until I can get a handle on why this is happening, I'll have to make sure I save stereo tracks to separate .wav files as soon as possible, then can import them back in. And also duplicate them on other RB tracks etc.