https://www.techradar.com/news/sony-claims-that-a-display-issue-on-its-xperia-phones-isnt-a-defect

Some users of the Sony Xperia XZ2 and Sony Xperia XZ1 ranges have reported an issue with the screen where if they repeatedly rub or touch it, visible lines or dots might appear temporarily, but according to Sony this is due to a characteristic of the display.

In a statement to Tweakers, the company said: “due to the characteristic of the display, you may see stripe patterns as a result of electrostatic in some models. This is not a functional defect and usually the stripe patterns fade away as the electrostatic disappears.”