BATTLETECH - UHD performance much slower than expected

[Statue]

One line summary of your issue
UHD performance much slower than expected

Please explain your issue is in as much detail as possible.
In 1920x1080, I get around 60FPS. At 3840x2160, I get less than 1FPS, even when just playing video.

Steps to reproduce the issue
Start the game at 1920x1080 resolution. Under Settings -> Video, change the resolution to 3840x2160, and try playing the game.

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[Statue]

I guess in lieu of no one responding, I figured out a work-around: If you use the Battletech Launcher, and set the display to "Exclusive Fullscreen", it plays at a normal speed in UHD.