Strange display flickering when using an external display

Hiya,

Been noticing a very strange display issue recently with my MacBook Air M1, 2020. When plugged into an external display using an official Apple HDMI adapter and no other peripherals, if I move an app with darker tones (a good example would be Outlook in dark mode) I notice a really strange flickering happening on the external display when I click back to gain focus back on my Mac's display. It only appears when the apps on the external screen are not in focus and I'm on the Mac's display doing chores. It's only noticeable with darker tones, like dark grey, however if something white is on the screen I notice faint lines appear, meaning it could be a power issue? I'm certain it isn't a problem with the cable, display or the adapter, as using all of those with a desktop PC shows no problems and the issue goes away.

As an aside, I've tried swapping the cable and adapter and, again, I've used another computer and that has no issues with the display. I'm running the latest version of Sequoia (15.1).

Any help would be greatly appreciated.

Thank you!

Grey360