Yup, i quit Proton (Mail) for the same reason. I had been using it for a long time… There are so many little bugs and annoyances, it’s frustrating to see new features being released all the time while obvious bugs and shortcomings are not fixed.

It was a very big relief going back to a normal email client.

I still support Proton (i pay for Proton VPN) and hope they will succeed in their mission.