You've got an unbelievable amount of errors in the log. Maybe it's because of it being Feb version. Have to go through them and compare with Feb source code to see if there's this much difference in the source.Screen goes black for 2 seconds, like restarting system UI, then to Lockscreen where I have to use Fingerprint to unlock. Only happens with my Pixel 3xl, no issues with my P6P.
Will probably take some time to check them all
Edit: I'm also thinking about a shortcut: if your mother is interested only in the battery, I can make you a battery-only version