How to open door for final boss (necrodancer) in singleplayer?

[poVoq]

I am running on Linux and finally (finally! :( ) beat the dead ringer just to be stuck in the entry room of the necrodancer boss battle as it seems impossible to open the door.
I assume you would normally do it by controlling the two characters seperatly and step on those two plates, but I am doing a single player run and the characters only move directly side by side.
It seems therefore impossible to open the door and I also did not find any controls/settings allowing to switch between the characters or controlling them seperatly.

[AviiHyrax]

The two characters are intended to be controlled at the same time; in order to shift their positions, you must use the geometry of the room to have one character stay in place while the other one moves.