Legacy project nightmares

I had an 8.5.3 project from late last year that I just needed to add a bit more to, so thought I'd just finish it off in X1.

HUGE mistake.  It opened fine, let me make my changes and everything seemed fine.  Then, as usual, my Tascam Fireone disappeared randomly, my Kore 2 NI Hardware Service crashed, and my Midi controller was no longer being recognized in X1, so I saved out of X1 and rebooted.  I came back in and now I can't open the project in X1 or 8.5.3. I try to launch it in either version and I get the forever hourglass.   If I hold down shift key and come in, I can get into the project, but without loading the key plugins in the track.

Assuming I can figure out which plugin presets I started with and all of the subsequent modifications (huge assumptions, given the 18,000+ presets of the hundreds of plugins on my system), there is almost no way I can recreate this.  Fortunately, I have a backup in a safety deposit box, but if this had been slightly more recent, it wouldn't have been backed up.

The bigger issue is that legacy projects from 8.5 are very unstable in X1 in my experience--often crashing at save or close.  Hopefully this has been looked at in the next patch, but given the many hundreds of projects I have it is a huge concern.  I REALLY don't care to live in the two worlds of 8.5 and X1 simultaneously, given the vast differences in operation (keystrokes, layout).  I've committed to X1 because it is generally better-designed overall despite some major steps backward in usability in some areas.