I upgraded to server 2022 and that fixed the issue.
So it looks an update on server 2019 is the culprit or the rendering on the 2022 is better as I see there is new driver for the hyper-v video adapter.
Is Hyper-V RDP display slow compared to Host OS?
I am testing Hyper on different servers and I noticed the login to guest VM RDP, will always be slower at the begin of loading the display contents.
Normally this should take less than 1ms to load, but in HyperV VM is could take like 2 seconds, is that normal behavior or there is a tweak I am missing?