Abrasion

In advanced stages, fabric or even thread becomes exposed and damaged.

Cause:

While moving, the belt contacts a foreign object in its path, such as a flange or bolt. This may be caused by improper belt tension or by the belt vibrating between the two idlers.

Solution:

Replace the belt and ensure that the belt tracks perfectly as it rotates around the pulleys. Check the tension and ensure that the belt is properly tensioned.