Home & recent apps buttons failing, and screen lock password problems - Samsung S6


AC Question

All of a sudden (i.e., no new apps, software/systems upgrade that I know of, setting changes, ect. ... though I was in the middle of hot-spotting to my laptop) ... my home button and recent apps button stopped working. Recent apps soft-key lights up, but does nothing (short tap or long) ... and home button is dead too.

Also finger print to get past lock screen works for a while (so that part of the home button works), but then phone starts asking for password to unlock, and then once unlocked, immediately asks me to reset back up password. (It also stops me in the middle of an open app to ask for a reset backup password.) So, this seems to be related to security/unlock settings ... whether I set it to fingerprint or swipe pattern, after a few mins/hours (variably) of the phone starts asking for password to unlock and then reset password once open.

I've tried:
- reboot (full power off)
- clear cache partition (done that just once)
- disabled Android Device Manager
- disabled fingerprint to unlock

Don't think it's a hardware problem, because after reboot (restart or full power off), the home and recent apps button works for a while (10 mins, 30 mins, even over night once - so 12 hours or so) ... but, then, suddenly, they will stop working and the phone behaves as described above.

Driving me nuts. Don't want to do a factory reset, if I can avoid it.

Any ideas?