Extruder motor stuttering


Yesterday 2 of our printers failed their prints and now the extruder motors are stuttering like this: https://onedrive.live.com/?authkey=%21ACuUcfPbAH_aup8&cid=AE8C523DAC464B94&id=AE8C523DAC464B94%21136062&parId=root&o=OneUp 

How can it be that 2 printers fail with the same problem at the same time?  :D A weird coincidence.

Can someone please confirm whether this could be a problem with the the stepper motor itself? 

We tried a completely new ribbon cable and the problem was still there.

Thank you in advance.

I don't think there is any problem with the steppers. What happens when you try to unload the filament? Are you using z-branded filament or something third party? Do you change the filament with unloading it and loading the new one or cutting it and loading the new one?

Try to remove the ribbon cable from its socket and put it firmly back again.

Move the Ribbon Cable around a bit and see if it the problem persists. As unlikely as it is you might have some bad ribbon cables or cables that run from the PCB to the motor.