[tatteredscroll]

Finally got the USB UART a full 60 seconds worth of output. Should be enough to track at least two boots. Not sure what I need to look for. When it was powered off (at least it appeared that way to me) and I briefly pressed the power button, I got this and it didn't do anything else--

Android Bootloader - UART_DM Initialized!!!
[60] disable otg power
[560] Going down for shutdown.

Afterwards, I pressed power for about 2-3 seconds and it started boot sequence.

//

Line 1486 I see this
[ 12.266075] init: [libfs_mgr]fs_mgr_mount_all(): /dev/block/bootdevice/by-name/userdata is wiped and /data ext4 is encryptable. Suggest recovery...

And further down, it looks like it's trying to reboot to recovery on its own, but my guess is it's not there?? so that could be causing the boot loop...