Multi-Rotation constraint weird rotations on Play

I have a character (rotated by 90°, this gives problems) with a cube in it, which I use to rotate the head (this is to simulate a camera rotation).
6481777--728203--upload_2020-11-2_10-47-27.png

6481777--728206--upload_2020-11-2_10-48-13.png

The cube and the head are already rotated in the same direction
6481777--728212--upload_2020-11-2_10-48-55.png

But when I press start the cube gets rotated by 90° (this happens at any rotation of the character, it's always 90°), and so does the head
6481777--728221--upload_2020-11-2_10-49-51.png

If I move the cube out of the character this does not happen.

If I move the cube out of the character (in the scene root) and set its Y rotation under 90° it stays like that on play, if I set anything above 90° it gets clamped to 90°...

In another similar setup I have the CameraPivot instead of the Cube and a Cube instead of the Head:
6481846--728233--upload_2020-11-2_11-22-13.png
the CameraPivot and the Cube both starts at (0, 0, 0) localRotation, while the Player is rotated to 100° on the Y
6481846--728236--upload_2020-11-2_11-22-59.png

6481846--728239--upload_2020-11-2_11-23-5.png

6481846--728242--upload_2020-11-2_11-23-15.png

As soon as I hit play the cube snaps to 100° while CameraPivot stays at 0°
6481846--728245--upload_2020-11-2_11-24-6.png

Checking or unchecking Maintain Rotation Offset does nothing...

If I rotate the Player to (0, 0, 0) everything works as expected

It almost seems like it is setting the localRotation of the constrained object based on the global rotation of the source