Front roller bar squealing loudly and harshly (began months ago and has grown worse and worse with time), creating black dust, and you cannot walk as it hangs up often and randomly, making it very unsafe! Engine running fine, everything else seems fine. Husband thinks it is the front roller bar and would like to order new one but needs instructions on how to take it out and put in new one. Is he correct? Help please! Miss my treadmill!