Mismatch between selected email and displayed email, and other Mail wonkiness.

Over the last week or so I've been experiencing a lot of issues with Mail and my iCloud email.

There's been a mismatch between the selected email in the middle column and the displayed email on the left.

I've also seemed to have lost several emails that I know I never deleted… except maybe they got deleted when deleting some other message that was being mismatched as above.

After restarting and app and the computer several times, I tried "rebuild mailbox" which seemed to temporarily fix the issue, but only temporarily. I also noticed that when I did this some emails in my inbox just disappeared, which now has me concerned for my entire email history.

Please see the attached screenshot.