Hello, There is no maintenace required. Some people like to oil the walk belt, The manual say to do this annually. To do this you loosen the walk belt and applty some synthetic oil to the walk board under the walk belt, then tighten the belt and the belt will distribute the oil where it needs to go. As far as the walk belt, just make sure that is stays in the center of the walk board. Now your front roller and drive belt. The roller does not get serviced, it has perminently sealed bearings. The drive belt usually lasts for many years, if you remove the motor hood and see alot of black dust, it will be the belt. At that point you need to see why it is comming apart/rubbing. After you determine that, you would want to replace it.
The slipping you are describing could be the drive belt slipping on the front roller or the drive pully on the front roller. To find out you need to remove the motor hood nad get on it and look. What you will be watching is the drive belt as it goes from the drive motor to the drive pully. When you try to stop the walk belt you will either stop the drive belt or stop the walk belt. If you stop both, the drive belt is at fault, if the motor keeps turning. If you stop the motor, the motor or the controller is bad. If you stop the walkbelt and not the drivebelt you have a bad drive pully on the front roller, and need to replace the front roller. When you do this you need to remove the drive belt, this is a ggod time to replace it.
Hope this helps, rate my solution if it helped you. Thanks, Matt
If you need further help, I’m available over the phone at https://www.6ya.com/expert/matt_8dbc24bf722649ac