1. There are sticky substances on the drum core, such as grease, etc.
Solution: Wipe the drum core with a clean soft cloth

2. The powder is not filled in properly.
Solution: Fill the powder carefully and don’t add too much at one time

3. Poor toner quality
Solution: Choose good quality toner

4. There is a problem with the waste toner scraper (such as scratches, aging, etc.)
Solution: Replace corresponding accessories

5. There is a problem with the powder bin scraper
Solution: Replace corresponding accessories

6. The drum core is damaged
Solution: Replace corresponding accessories

Attached is a schematic diagram for replacing the toner cartridge OPC（Organic Photoconductor）: