Okay, bootloop after over two years of use. Managed to get it to reboot after applying pressure while booting, but the effect short-lived. I believe that the best procedure would be to remove and resolder the RAM chip sitting atop the 808, but since I have not the smallest hope of carrying out such a specialist procedure, I'll try the old hair-drier method, then put something between the chip and the shield to apply a bit of pressure. I am quite confident of a bad result.
If perchance it works, I'll let you know for how long. Get ready to laugh.
Later: Hair-drier no go, so I applied a lighter flame to the chip for twenty seconds or so. Successful boot. At least now I can be sure the battery is charging, which I wasn't before.
Few minutes later: fail.
A few days later: Full boot after a longer application of a lighter flame, for perhaps a minute.
Couple of days later: Fail, when granting an app a location request, though whether relevant, I don't know.