I don't think the amount of weight factors in too much as I first noticed the motion using the ETX90 where two counter weights at the very top of the bar will balance it.
The second video Mario posted in his second post showing an allen wrench in the pulley is what I notice when just watching the small pulley, a stop start motion at the 1.3 second interval. It never bothered me as I thought it was just the electronics sending pulses to move the motor in steps as it tracks, instead of a steady movement like you find in the old C8 synchro motors. It definitely though does correspond to the sound of the electronics, the pulsing hiss that is heard as it is tracking.
Dawson Springs, Ky
Scopes: Meade ETX90RA(deforked now) Sky Watcher 150MCT
Camera: ZWO ASI 120MC-S
Software: Explore Stars Android, ASCOM, Stellarium Scope, Stellarium, AS!3, SharpCap, RegiStax6.