I'm also getting tasks repeating, so on a given calendar day there may be as many as a dozen of the same task or event, instead of one. I turned Sync Service off, that may help, but now I have a gazillion items to delete.

Is there any way to either export the last 2 years of my calendars, delete them all and import the calendars, or to do mass deletions of calendar items before 2 years ago?