What takes place during an iPhone hard reset?
I do not know for sure that this happens but I was told that in order for IOS to do anything except just it's usual booting functions you actually need to do a hard reset three times in a row.

Not sure why, and this was advice I read (don't remember where) several years ago. Perhaps 3 hard resets in a row trigger some sort of flag that forces IOS to do some special maintenance, not really sure but I am throwing it out in case someone else has heard this or knows is it complete and utter BS.