It's genuinely disappointing. I focus on all 4 slots and now it seems there is no point in doing so at all. The game should remain the way it is (4 slots per manager)..Or add up the points and stats of all 4 slots into 1 but that wouldn't be fair to those who solely focus on less than 4 slots.
Having said that, I think it's a bug and It'll be sorted soon. So keep playing and keep checking till it sorts itself out and keep this topic alive.