Kettler Model Kinetic S3 Rowing Machine rope snap want spare rope

Is this a common problem with the axis rower as I the machine has been little used since purchase in August 2013 having to be replaced at the end of September 2013 following the cord snapping. a new model was provided and the same problem occurred after only 20 hours use. The cord has frayed and snapped 15 inches from the handle on both occasions. I m reluctant t have a heavier cord fitted as it would be thicker and surely would have a negative effect on computer calibrations. Is this a common problem with the axis rower as I the machine has been little used since purchase in August 2013 having to be replaced at the end of September 2013 following the cord snapping. a new model was provided and the same problem occurred after only 20 hours use. The cord has frayed and snapped 15 inches from the handle on both occasions. I m reluctant t have a heavier cord fitted as it would be thicker and surely would have a negative effect on computer calibrations.