HTC U11 has a persistent problem that cannot be solved, you can perform a factory reset (also called a hard reset or master reset).
A factory reset reverts
HTC U11 back to its initial state—the state before you turned it on for the first time.
Important: Apps you've downloaded and installed, your accounts, your files, as well as system and app data and settings will be removed. Be sure to back up any data and files you want to keep before you do a factory reset.
Home screen, swipe up and then tap
To avoid deleting media and other data from your storage card, make sure you do not select the
Erase SD card option.
Note: A factory reset may not permanently erase all data, including personal information.