My S5 started to make some unpleasant noises when the print bed moved up and down. The issue was in my case that the white plastic cover at the back of the print bed carriage has deformed over time. One of the through holes in the plastic cover moved and was now touching the z-axis rod.
This could also happen to your S5 printer over time. I will try to explain what I did to solve the issue. I also took some pictures from the parts inside with some comments.
Before the repair: