I have adjusted the matt, lubricated it, tried it 20 times, phoned York and no help at all. The matt slips or judders so you can feel it in your joints - can't be good - only 2 years old so can't afford to replace it. It is a York Z16 fitness treadmill.
i dont know what york fitness number you have been phoning,but i found this one to be very helpful and can also deliver any parts you may need at a very reasonable price.01327701824.hope this helps.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix gym/fitness equipment.