1) uninstall/reinstall won't fix anything if you re-use the same Gimp profile (and I don't know if CCleaner can clean that). Of course if you go from 2.8 to 2.10 your Gimp profile is at a different place... but the 2.10 installer will migrate the 2.8 profile to 2.10 and this could migrate profile problems as well.
2) 2.10 is fairly stable by know, but not all plugins have been ported to it
3) you are the one who knows. If you installed plugins properly the additions are in your Gimp 2.8 profile so easy to spot
If you tell us the error message we could make suggestions to fix the problem. On the other hand, on an ancient computer, it could be the computer having hardware problems (I don't trust a HDD over 5 years old, and a SSD over 3) and installing a new Gimp isn't going to fix things.
_________________
|