Rekordbox volume sliders disappearing in 4-deck mode

Using Rekordbox 7.1.0 with DDJ-1000 controller.

When switching Rekordbox to 4-deck mode (horizontal or vertical doesn't matter), only the volume sliders of the 2 currently active decks show up in the mixer section of the software. The other 2 remain completely invisible and there seems to be no way to make them show up.
It does not matter which are the 2 active decks upon the mode switch, those are the ones showing up. Switching active decks while in 4-deck mode doesn't change anything, only going back to 2-deck mode and swapping decks can make other sliders visible. But never more than two.

I am unsure which Rekordbox version introduced this problem since I haven't used the software in 4-deck mode for a while. Only found some old Rekordbox 6 footage showing it was definitely not the case back then.