Yes, I believe I had the same problem. In another topic
I found a discussion of the Z axis pulley set screw. I found mine tight but not tightened against the flat spot on the motor shaft as they were discussing. When I took it off, I did see evidence of a slight groove (more of a scratch) on the motor shaft. I put the pulley back on, but not so far as to have the setscrew go past the available flat area, and tightened it there. I’ve only done one experiment since, but it looks like it took care of the Z-axis variation.