Without doubt, the biggest ongoing frustration I experience in bands has to do with scheduling rehearsals.
Once you toss out there the fact that this is a hobby, nobody prioritizes their commitments to it at all. So I live in a world where I'm continually setting aside time for rehearsals that get cancelled or moved. Then you set aside the new time, and that also gets cancelled or moved. Multiply this effect by a factor of however many bands you are in, if you are in more than one, and the number of people in them, and you find yourself unable to commit to anything else but also, somehow, simultaneously always having your time free at the last minute.
It's a joy, for sure.