Moving my email via IMAP bridge into ProtonMail resulted in many many messages being corrupted (they show HTML as TXT instead of rendering it) and duplicated.
I finally literally gave up a week ago and switched to Fastmail and am already so much happier. It's annoying, I really wanted to love Protonmail but they just do this window dressing nonsense with updated logos and website design instead of making the core product work better. I can't deal with it anymore.
It's very sad to me, I was one of their first customers :-(