Random password reset without 2FA

I am having an odd issue. I randomly get a notification email that my apple id password has been reset every few weeks, even though I have not reset it myself. My devices that are already signed it seem to work and do not ask me to re-enter the password.

When I try to log into a service with my known password, it does not work and I need to reset it. It asks me for the two factor authentication code, which I receive on my device and everything works fine afterwards.

When I get the email of the password change not initiated by me, there is no 2FA popping up on my devices.

What could be causing this?