I am having the most frustrating problem. I have a 2019 Macbook Pro (AMD 5500M) running Windows 10 / Bootcamp. I have a 4k UHD external display which will not display above 30hz. I thought it could be the cable, but somehow discovered that when the laptop lid is open, both displays will run at 60hz! I close the lid, and the display switches back down to 29hz. There is no way to change this.
This problem ONLY occurs in Windows 10 / Bootcamp. This does not happen on Mac.
Here are the screenshots for the monitor settings
Other things I have tried
Just disabling the monitor in the display settings (use only thing monitor). That also changes the display to 30hz.
I have looked around the power settings thinking there is some strange video switching, but i can't find it.
Any help would be VERY much appreciated.