Thanks for the input!
It seems I solved the problem. The scratch disk that Resolve was using was almost completely full. I freed up 2 TB of space and now Resolve seems to be behaving. Also, I was able to export the project and reimport it to a new project.
I have not tried the Save As... and loading the Backup files. I will report how that goes.
I wish Resolve would let me know when the scratch disks get so full that it can't function properly... but it also is part of good housekeeping I guess...