Slight crop on my reference monitor

I have an issue where the outer 2% of my image is being cropped off on my external monitor (LG OLED 55C connected to Decklink Mini 4K). I tried changing the image scaling settings, but to no avail. In the GUI monitor the image is scaled correctly, but my reference monitor is cropped.

Anyone know what could cause this? All resolution settings are set to 2160p.

The TV itself might have overscan/underscan settings.