EDIT 3:
Please contact me vie the eMail provided below and share the logs when it happens - Without logs I can't debug it as I don't face those frequent logout issues you are describing (I did in the past, and I applied some fixes to prevent it. Without logs, I don't know why you face those issues)

EDIT 2:
This should be fixed in v1.11.3 alongside with 2FA being available on the free tier as well now.

EDIT 1:
This is not supposed to happen - if you could share some logs, then I can sort this out.
Please contact me: support+mcpm@olausson.de

Thanks a lot for this spot on summary and the 5 star rating of my extensive! I am glad it works for you. I myself had been a heavy Checker Plus for Gmail user before I switched to Proton. I missed it so much that I had to make a similar (still not as polished as Checker Plus) extensive for Proton!