As best I can see there aren't any pulleys popping. There is a clunking noise at times. I think the noise is coming from the motors.
If I turn off the power and push the head around it doesn't feel completely smooth but I wouldn't say there is a lot of resistance either.
I have tried another computer and the same problem recurred.
When the firmware was installed it was done from a Mac, but it worked fine with the PC I am using after that.
I had the speed set quite low (20mm/s), could this be part of the problem?