Force Feedback Calculation

Force feedback comes straight from the physics steering rack, there's no post-processing that takes into account the speed of the car or anything.

Can you try in Safe Mode, to rule out the possibility of mods having broken or modified how ffb works?

 

Please record a video of the issue that shows front tires, the FFB Graph ui app, and the Steering ui app.

 

I'm afraid the video does not show the front tires, nor does it show the FFB Graph app.
Can you attach your modified vehicle config? And which exact roller variant is it? + the video as described in my previous post.

 

Anyway, here I get some sideways movement, which is normal because it's impossible for the car to be perfectly aligned. The rear of the wheel is trying to align the car, while the fronts are staying firm on the ground. At least in my case (I don't know what your front wheels are doing, you cannot tell by the video you uploaded). So it looks normal to me.

 

Thanks a lot. Yep that's perfectly normal. In real life, the rollers would be actual rollers (rather than ice-like surfaces), and the car would need to be firmly strapped both in vertical direction and in horizontal direction, to prevent any unsafe movement.
So with your test conditions, it's perfectly normal that the car will be moving all over the place, and therefore generating ffb forces when the front steering rod is pushed sideways due to suspension caster.