Phone app random logout?

I'm very new to the phone app and thanks to the forums here figuring out what works and what doesn't, thanks. One thing happening to me I haven't seen discussed is it seems about every 1-3 days the app insists I log in from scratch. I set it to stay logged in and have enabled fingerprint scanning, but some times it insists I go back to the username/password, it won't accept a fingerprint scan. The rest is a mix of not needing anything or the fingerprint scanning being OK. I'm assuming that is some kind of timeout.

Logging back in again is fine. A bit annoying, but not stopping me. I'm mainly asking so if there is something I'm doing to make it forget the login credentials that I can stop doing. I'm sure there is logic, but to me it seems random.

I'm using Android on a fairly recent Samsung S21. I also turn my phone off every night, but the need to log in doesn't seem correlated to that.

will