That's true, I've seen rackets strung on high end machine strung badly. It probably the operator's fault or bad machine mantainance. I've always said that all machines do the same job, it's all a matter of simple you want that job to be.
A poorly maintained machine is more like to break down or cause damage to the racket.
Machines: Gamma 6004 2-point w/ Wise 2086 & Babolat Sensor Dual