I also got a pinebook pro and I managed to use it a sum total of 12 times (and only on flat surfaces with the power plugged in because otherwise the screen would flicker like a strobe light) before the screen completely gave up and now it's an expensive paperweight.
Still I will keep buying these things.. eventually someone will figure out how to make reliable laptops that align with the ethos of free software. I've researched system76, puri.sm and also lately the way too expensive MNT reform, but really the only laptop people seem to be happy with is thinkpad x220 / x230 which came out 12 years ago.... This makes me sad.
I would pay a lot for a super sturdy laptop which works (and aligns with the free software ethos).
One of the possible root causes for those symptoms might be dried up (or wrongly applied) cooling paste between the heatsinks and the CPU/GPU.
I highly recommend trying to replace the cooling paste, this may fix all your issues.
I recently did this on my 2 year old Asus laptop and it feels like I just bought a new machine. It went from unusable to I won't have to buy a new laptop for a couple more years. It cost me 10 EUR and maybe half an hour to get it done.
You won't ever have an issue with dry paste, and from what I can tell the CPU/GPU only runs a degree or so hotter than when using premium thermal paste.
Stock paste goes for longevity and cooling, so it's kinda crummy at both.
Thermal pads go for longevity with a sacrifice to cooling.
High performance paste like arctic silver goes for cooling over longevity; but can be re-applied many times as it doesn't damage hardware.
Liquid metal like Thermal Grizzly's: conductonaught, goes for extreme cooling at the expense of hardware. (IE; it will literally eat your computer, slowly, over time).
According to a Linus techtips video on Youtube the difference is not really measurable. So I kind of tend to think that a high quality thermal pad is just simply superior in every way. The only reason I didn't try it, is because I couldn't find any in stock.