Why is my monitor backlight flickering at a slow but constant rate?

I have a Dell S2417DG and recently I brought it with me back to Australia. Today I plugged it in but noticed that while everything worked fine and there’s no damage to the device that I can see, it is having this weird issue where the backlight would flicker slowly but constantly. It’s at 100% brightness for 3 seconds then it would dim a little and stay there for another 3 seconds then return to 100% brightness and back and forth.

I suspected a power issue at the hotel I’m currently in but the device do support 110-240V 50-60Hz so that should be compatible with the voltage in Australia. It does not seem to be video output issue as well - the same flickering happens even with my computer unplugged and with only the OSD displayed. All other aspect of the monitor seems to be working just fine and no damage to the exterior shell as well so I was not sure what is the issue here.