As belows reasons FYI:
1. Thermal paper quality issue
2. Print head need to be cleaned
3. Need to setup print content,font size or printer parameter(such as higher print temp or lower the print speed etc)
4.Print Head quality issue.
Contact: Cindy H
Phone: 0086-13727008595
Tel: 0086-0756-6835803
Company: Zhuhai CDHlighting Co.,Ltd
Add: Fushan Industrial Park,Doumen District Zhuhai.GD.China
Cindy H