Cubase 11 Pro - corrupt project?

This is a new one for me. A 10.5 project, opened and saved a few times in 11. I recorded two audio tracks together in a folder (vocal - 1 dry, one compressed) and when I played back, they were both out of time. I checked the tempo and everything else I could think of. The files looked to be in time. In fact, when I took them out of the Vocal subgroup and routed to the main out, they were in time. I moved on to another song but the next time I opened the file, I got an error message that Autosave could not work because the file was corrupt. I’ve tried a few ways to get this song back. I went back a month, created an archive, but when I imported some old files into the project (not the vocals) it crashed the next time I opened it. What I can try next is using a new template and importing files - I’d really like to get the drums back and they are not yet bounced so many lanes etc. Has anyone else experienced this? Ideas? Thanks very much.