Okay, this is just weird.
I have a second Pro1x that I have kept on Stock so that I can try and answer questions about stock. I have tried to make sure I charged it every so often, but, sure enough, during another very hectic time, I failed to do so and it would not turn on this morning.
So, I plugged it in (using my usb cable from my Pixel plugged into an Anker fast charging wall plug, if it matters, not the FxTec brick). It booted up, showed 1% battery (first mystery... how was it able to fully boot at 1%) and said "charging rapidly," Then the screen went off. I figured, that w