I have two users who have the exact same issue but its not 100% reproducible. The event is pretty much any multi-person reoccurring appointment. When the person wants to open the individual occurrence not the reoccurring event to decline that weeks meeting they get the message:
"Sorry, we're having trouble opening this item. This could be temporary, but if you see it again you might want to restart Outlook. You changed one of the recurrences of this item, and this instance no longer exists. Close any open
items and try again."
That same user can sign into a different computer and the error moves with them. I have tried running an online repair and rebuilding the outlook profile. Also on the machine they are using I have disabled cache mode and that didn't resolve
the problem either.