You mentioned you corrected a little bit of battery corrosion?
Where there is some there is possibly more, under chips etc that maybe you haven't spotted?
Can you take a closeup (clear) picture of the area below the battery pack?
I wouldn't overthink this issue as you could be running off on tangents that are unrelated.
Battery corrosion is far and away the most common problem with these boards and it causes lots of differing outcomes that can be misleading. You already mentioned that you had "some" - I suspect more.