bugged summer quests-party issues

Since summer update, some people have been experiencing the following issue (s):

1. getting kicked from party a few minutes after they join, even if they have not started a coop quest, with error "player x is not logged in"
2. when trying to start coop quest, even though they click accept, the box just disappears and nothing happens and/or getting the message "city needs to be at least lv 3 for multiplayer"
3. when player joins party they can see his name but not his shield and cannot see which quests they have in common, coop quest won't start.

I believe some of the new summer events are causing this bug. After abandoning the solstice elephants ones, the party issues disappeared and I was able to coop. This solution worked for a couple more people who had the same issue. However, today I'm experiencing the same issue again. I had to abandon all summer quests to be able to join party.