Because of MBS-11569 there are over a hundred collections that have both releases and release groups in them, despite them being either release or release group collections (MBS-10857).

We should run a one-off script that drops any entities from a collection that do not match the type of that collection. There might be some cases where the only entity in a collection doesn't match the desired entity type - in that case, we could consider changing the collection type instead of removing the only entity.