Guess I'll answer my own question after messing around with the shaft to find the culprit.
I've been making an abnormally steep catch than normal for me lately. That's fine but forgot to do one thing; I didn't raise the elbow higher but just manipulated the top hand in a funky downward position for a vertical catch. So everything wasn't actually in line(shoulder, elbow and wrist) like I perceived. I think I've given the advice to others but am not following it obviously. Anyhow this funky un-ergonomic hand position gave the shaft a chance to put a lot of pressure on that thumb knuckle which caused a nasty sore. It never ends and is never the same, that's why it's so addicting : )