Sony has officially responded to user reports of a striped pattern or spots on the screen of some Xperia XZ1 and XZ2 phones — including compact models. These patterns sometimes started randomly but could also be recreated by rubbing the display and would generally dissipate over time.
Tweakers, a Dutch technology website, received a statement from Sony stating that "Due to the properties of the screen, some models may show stripe patterns due to electrostatic effects, it is not a functional defect and usually the stripe patterns disappear when electrostaticity disappears." (translated to English). PhoneArena has also found that tapping on the screen multiple times can speed up the display's return to normal.
It is unfortunate that Sony can’t provide a solution to the problem. This is likely to be related to the design of the phone or the display hardware and is therefore likely to be something that can only be fixed in as-yet-unannounced models like a future XZ3. Owners will be partially relieved to know it isn’t a sign that their phone is about to die.