Yeah, it seems that the limit before corruption is 10K on two Mastery and 12710 on one Mastery. If you attempt to add even 1 more point after 12710 on any other ones, it'll crash the save.
I only found that after 12710, you have to start using the points you earned on missions after that. I did the first mission, earned 1 point, and used it with no problem. But if I add 1 more, it'll crash.
So yeah, it'll be interesting to find out how to overwrite them directly. It takes me about 7+ Hours to apply 10K on each Mastery.
@petterhung Were you the one that helped Save Wizard to apply MAX AP on their list? I'm just wondering if it's worth re-applying the Skill Points with their method. If they're the same, I would probably run into the same bug.
I think either way, people may encounter the crushing BUG when using more than 32710 artificial points made from modifying the save. I'm going to do a fresh save with Save Wizard's method tonight and see if I get the same crash bug.