pbp no longer boots

[xyzzy]

If you get boot logo, then the kernel is starting (if it's the bootsplash), or userspace is running if it's the desktop starting screen. So you've gotten significantly farther than u-boot. That really points to a battery problem. Power draw will go up as the GPU is enabled and all the CPU cores run stuff during start up, where you had the crash. One could try measuring battery cell voltage and see if it's dropping too low. There's an alarm signal for SOC and RTT on the battery monitor. Too bad they don't go to a LED.