Intermittent Boot Issues
I haven't had the opportunity to install the new U-boot, since (as I understand) I'll need an external keyboard for that and I haven't one on-hand at the moment. However, I have found that the device usually boots up just fine if I hold the power button for longer, usually a second or three after the power indicator actually lights up.
It makes me wonder if the issue isn't the boot-up so much as how the Pinebook Pro's default U-boot handles the machine's indicator lights. I encountered similar problems with the indicator lights while attempting to disengage the Wifi privacy switch, and the solution to that problem (holding the keyboard combo for a full three seconds rather than just until the indicator lights up) was what prompted me to try holding the power button for longer while booting it up.
If anyone else is still dealing with the default U-boot, I'd be interested to see if this works around the problem for you too.
It makes me wonder if the issue isn't the boot-up so much as how the Pinebook Pro's default U-boot handles the machine's indicator lights. I encountered similar problems with the indicator lights while attempting to disengage the Wifi privacy switch, and the solution to that problem (holding the keyboard combo for a full three seconds rather than just until the indicator lights up) was what prompted me to try holding the power button for longer while booting it up.
If anyone else is still dealing with the default U-boot, I'd be interested to see if this works around the problem for you too.