My Z-baseplate would not level consistently using the Z_TILT_ADJUST routine in Klipper. The leveling would not converge or start diverging after the 6 iterations. I had to resort to manually turning the Z-couplings to pre-level the stage. I used a tri-square to measure the baseplate height to the top of the frame, turn the couplings until the bed was close to level then Home All.
I noticed that the Z-base did not want to be level. I would have to hold two couplings to keep the base plate level and press the Home button at the same time.
I did try loosening the Z- screws to the Z-frame, the red brackets to the frame screws and the red bracket to linear slider screws, block the Z-stage up so it was somewhat level, then carefully tighten the screws. This only worked for one day then the Z-stage warped back to un-level.
I noticed that the Z1 coupling (L R) would pull apart. This type of coupling needs end pressure to stay together. I had brass strip 6mm W X 0.4mm Thk X 750mm L that I cut into 36mm lengths then bent 3mm tabs at 90 degrees to make clips that would hold the Left Rear coupling together. I used a small cable tie to keep the clips in place.
Now the Z_TILT_ADJUST routine works correctly getting the bed to within .005mm of live in three tries.