I held off upgrading from V21 to V22 until I completed a project. Now I regret the decision to upgrade. I have to make a few changes to the drawings which are opening with a string of errors. Any edits result in disappearing title block and other issues. Fortunately, I haven't saved any work under V22. Wasted too many hours today trying other things. I would like to revert to V21 ... hopefully that will solve this problem short term. How do I do that?