U2419H, horizontal lines on screen

Hello,

My monitor has horizontal lines running across it.

My operating system is macOS Venture 13.4.1 and the steps I've taken for resolution are:

1. Default Reset (did not work)
2. Diagnosis
   1. Lines were not visible on Green & Red but were all other times (and of course when unplugged from my Macbook Pro

 Please can you confirm if there's anything else I can do or if it is a hardware problem.

Thanks,
Sam