Overreaction: thinking that the instability I was feeling meant there was a new issue. After a month of careful observation, it seems that the instability comes when I reach a new level in physical therapy, hangs around for a few days, then goes away and stays away.
Underreaction: thinking that the pain on my tibia was of the same nature as the instability. Turns out it's a stress fracture. X-rays have been taken, updates will be given as necessary.