GameCenter iTunesConnect - Leaderboard is not a member of a leaderboard set attached to version

Question

Does anyone know what does this mean? I've tried searching everywhere but can't find a word on it.

Essentially I created a group for an app (and its deluxe counterpart), then created some leaderboards and added them to leaderboard sets. Then I tried adding the leaderboard sets and checking their constituent leaderboards.

Unchecking all the leaderboards doesn't fix this and toggling off Game Center doesn't help either.

I can no longer save changes to the app and Apple hasn't gotten back to me (2 weeks). I do have a default leaderboard selected.