Ender 3 weird drop in bed level

I have an Ender 3 a 3DTouch, with the SKR Mini E3 1.2 board.

From one day to another the probe started producing this pattern, where the right side of my bed (5x5 mesh, tried with 3x3, 7x7, all produce the same pattern) just drops by a significant amount. The bed is the Creality glass bed. I tried switching it back to the stock Ender 3 plate (non-magnetic), but no physical sign of this drop can be seen by the eye.

Probe testing with M048 usually gave me Range ~0.005, and standard deviation between 0.001-0.0025 both in the problematic part, and any other part on the bed.

What could cause this problem?

• Considering this is an Ender, it is probably caused by the rollers on the X axis or the un-driven right Z post. I've seen behavior like this caused by a too constraint PTFE Bowden tube, at the far end the tube pulls on the carriage lifting it slightly upwards, hence a different/larger gap.
– 0scar
Feb 1 at 21:38
• unaigning the X-portal can happen Feb 2 at 1:08
• My understanding is the M048 probe test moves the z-position. Have you tried measuring how flat your bed is by not moving z and using a digital indicator (drop gauge) such as photos in 3dprinting.stackexchange.com/questions/470/bed-leveling-method/… ? Feb 2 at 12:44
• @0scar 's answer was correct, I had to tighten the eccentric nuts on my X axis and the problem is gone! Thank you!
– Syns
Feb 2 at 17:47