Since this was an isolated issue I believe your problem was an upload on a bad day for Ancestry. I would do as you planned and get a new Ancestry tree. Cleaning your RM database first is always a good plan.
I have completed the replacement of both my RM data base and my Ancestry tree. This appears to have solved the issues. I'm not sure which was corrupted. However, of course, reconnecting to a new Ancestry tree reset all my hints. These now have to be reviewed and either accepted or rejected (again).
Thanks again for your help