System Ui is probably your home screen or a system driven app playing up.
If you can identify what you're doing at the time, clear cache and data for the app in use but the best way to fix it is to back up and factory reset the phone.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
Please select the post that helped you best and mark as the solution. This helps other members in resolving their issues faster. Thank you.
