Reason:
1. The belt tension is too large.
2. Parallel misalignment of two axes.
3. The width of the belt is larger than the diameter of the pulley.
4. Overload.
5. Bad meshing between belt and pulley.
Countermeasures:
1. Reduce the tension force (no teeth skipping is allowed)
2. Adjust the positioning of the pulley.
3. Inspection design.
4. Inspection design.
5. Check the belt and pulley.