One ear flopped after 14 weeks old

My Doberman puppy had his ears cropped at 10 weeks old and they stayed glued onto the sponge for one week. Even with the cone he ripped it off so many times because of the itching that I couldn’t keep it on. To my surprise, his ears stood after that week and looked great. About a month later one ear flopped over whether from rough play with a larger dog or maybe from natural causes due to teething as I’ve read. First of all, how do I know which caused it and does it even matter? And second of all, should I begin posting or wait until teething is over, and if so, just the flopped ear or both?
First-time Doberman owner