It all boils down to how the driver's treat the machine. They are obviously abusing them. If your customer is paying the bills with no fuss, then all you can do is advise them. If your on a fixed maintenance contract, then you all have to sit down and have a frank discussion about abuse to the machines. Most drivers don't balance the load, putting a heavy skid at the rear.
Blown fuses are from pushing skids, overloading. Yellow single smoothy tires work best. I find the triple ones fails 3 times more!
Sounds like no one is cleaning the floors.....wood and plastic take their toll. As long as you have explained to the customer, you've done your part. They pay for their mistakes, and you keep busy!