How to judge and solve?
The possible reasons are:
1. Armature winding connection failure
2. Mica highlights
3. Commutator riser connection disconnection
4. The commutator is loose
5. Brush material does not match motor and load
Solution:
1. Find a manufacturer
2. Mica grooving or using wear-resistant carbon brushes
3. Welding at the joint
4. Tightening the commutator or rounding, rounding, mica replacement
5. Use the recommended carbon brush material and carbon brush structure

The Importance Of The Commutator
Then Why Do You Break Up The Commutator
Commutator Structure Type