Airpods "Share Audio"

Hello!

Me and my band (in total there is 4 of us) use two pair of airpods for playing to a click. For this, we use the "Share Audio" function. Everything worked great in practice but when we played a show trouble started. For some reason it was not possible anymore to click "Share Audio" and then add the second pair of AIrpods to the (already connected) first one but I could only switch between them, so that only one of them was connected at a time instead of both of them.

Did anybody else run into this?

Do you think it could be resolved by a Software Update?

And additionally.....do the airpods work with any Iphone model? I am thinking of buying an old SE from 2016....the airpods and the "share audio" function should still work, right?

Many Thanks in Adavance :)