Beacon mesh calibrate seems to be offset to the left relative to centre

Using RatOS 2.1RC3 and a Beacon probe on a RatRig 400.

When the printer is doing a mesh calibrate before print, it goes too far to the left and not far enough to the right. It even hits the x-axis end stop while doing the mesh calibrate.

The location it uses to do a Z calibrate is exactly in the centre, so the centre point seems properly defined. What could be the reason and what is the way to fix this?