I can't really tell, I had 4 symptoms of past problems suddenly escalating on day 6 last time I took the fast, and since then I never experienced them again (so far), so there might be something interesting going on. It's possible autophagy and fat burning might remove some "memory" but I have no scientific explanation for it. My theory is that as body doesn't have to fight all kinds of pathogens coming in from food, it can start correcting internal problems/mistakes instead with the same processes it normally uses to fight external threats.

Breaking apart old injuries...? Never heard of this hypothesis, how would this work?

Many people report feeling older injuries/illnesses during prolonged fasting. It's not clear what is the nature of that, if it's just psychosomatic and some neural pathway is correcting/readjusting/"backpropagating" itself (think phantom pain) or if the original repair was "temporary" and body does a proper rebuild there, or something completely different is going on. Try 1 week then tell us if you felt something similar, I did.

EDIT: This Reddit thread has interesting comments, elevated HGH might be the culprit:

https://old.reddit.com/r/fasting/comments/5gl1aq/can_fasting...