Airpods Problems with Connection

My Airpods have a very Strange Problem

If Connect them to my iPhone 7 plus everything is okay but when i start to Play music they disconnect after some some Seconds or a half Minute, so i have to reconnect them again

They both are 100% charged and whats very Strange is, that If i Just Open the Case, Connect them without taking them out and Play music they work Like normal but only when they are in the Case

I already checked for a Firmware Update, did a Reset and also tried them with an iPhone 11 and with an Android Phone