Bizarre refresh rate issues with mouse steering.

Hello folks,

I am getting this extremely bizzarre issue.. My game runs smooth, usually, but until recently, sometime back in late 0.24, I kept getting extreme lag spikes as if there was a memory issue.

So I kept troubleshooting, stopped playing until 0.25 released, thought maybe it was a memory leak or just some strange issue with my PC, and ever since 0.25 released, after even all the hotfixes, I still have this issue.
And now I have come to find out, that the issue arrises only when I start using mouse steering. If I keep to classic keyboard WASD, and don't move my mouse at all, game runs smooth at 40-60fps depending on map/cars/whatever else.

But as soon as I touch my mouse with the intention to steer, my FPS plummets, to the low 10s. And it seems like it isn't just the game, because the FPS counter doesn't go down at all, it still remains at whatever it was before I started moving my mouse. It's as if my actual monitor refresh rate plummets for whatever reason.
This only happens with BeamNG and NOTHING else. V-Sync is turned off fyi. Happens on even the lowest Graphical settings.

Monitor is capable of Freesync, which I think could be one of the causes since it seems the actual refresh rate of the monitor goes down, since if I'm quick enough and hover over my taskbar, the icons are choppy as well.

Could be monitor drivers as well which I haven't tried updating/reinstalling yet.

Fullscreen mode seems to fix it for most of the time (for whatever reason?), Borderless fullscreen and Windowed have the issue constantly.

Video showing the issue attached below.


EDIT:
Removing mouse-steering keybind doesn't fix the issue.
Neither does switching mouses.
Or running on my integrated laptop display, with the monitor unplugged.