Maybe it is just my pure luck but I just played online adventure playgrounds unranked and it was all fine at the end. Got Cr and XP so might be the only one which works. I was playing solo (if that changes anything) and joined online adventure playgrounds. hope that help to get 100% festival playlist (2 in the row all end screens ok points too)
Already tried this and still disconnects after the last race.
I think there is a way to join and get points. You need to wait for session where it will show only few players to join like 3 out of 4 or 2 out of 3. As that is what happen to me when I had it workin fine