Mac Mini M1 display issues through HDMI
So, I got the brand new Base Mac Mini for our video production company. It edits like a dream, so much quicker than our previous MacBook Pro's! I have 2 displays plugged in:
1x USBC/Thunderbolt3 24inch LG Ultrafine 4k screen (bought through Apple last year)
1x LG 27inch 4k display, plugged in via HDMI.
The issue I am having is that the 27inch display has a really horrible display lag, moving the mouse, dragging windows round the screen and anything I do on that 27inch screen just has a horrible lag. Even if I unplug my Thunderbolt 3 screen, there's still an awful lag via HDMI. I have tried 2 different 4k monitors and they are all the same. I also tried to calibrate the display using Display Cal and no luck, but that is less urgent. It's like I am using an old old very tired Mac when I plug in the display via HDMI. Any ideas?
Mac mini, macOS 11.0