I searched our online knowledge base and found two different articles below for lines depending on if they are horizontal or vertical.
Horizontal - https://www.support.xerox.com/en-us/article/en/1489783.html
Vertical - https://www.support.xerox.com/en-us/article/en/1490068.html
If you're still having issues after trying these steps please consider calling our support department for additional assistance.
Sometimes when I print a printed line that should not be on the sheet appears so it damages my document and I have to print it again. Is it a factory defect? Can I fix it?