so, I'm right in the middle of clicking "wait list" and the refresh hits... some premade I was going to join disappears... others I have joined and they say "pending", whole line turns green... then they disappear from oQueue entirely... only to come back 30 seconds later in the list, but I'm back to "wait list"

extremely frustrating...

Use the filters to reduce the # of groups you see in your list:



Hold the shift key will pause your list from updating.
Once you waitlist for a group it is possible the leader did not want you and removed you from their waitlist.