Why are there white spots/white stripes on label？

Situation: If there're some irregular white spots or white stripes which causes barcodes fail to be scaned, it might not print correctly. 

Reason ①: Dust or paper scraps on the printer head 

Please clean the printer head with the alcohol swap by referring to the link: 

https://support.pedoolo.com/support/solutions/articles/151000077804-maintenance

NOTE: Dust,glue or other materials might be stuck to printer head after frequent printing or due to the shipping or storage in warehouses.Inspect the print head for contaminants and multi-clean it cause the glue may not be easy to clean.

Reason ②: Dust on the label surface

Please keep the labels well. 

Reason ③: Poor-quality label paper 

Please get labels in better quality.