Shadows performance on RX 6700 XT

Hello there,

I buy a new GPU month ago, the RX 6700 XT from AMD.
It works pretty well on every game except on BeamNG.
To give you an idea, I had an RX 570 and the performances are almost the same (which isn't logic).
After having tried a lot of workarounds, I finally found a way to fix my performance loss: Disable the shadows !
I don't know how to explain that but the game in 'High settings' run at 50-60 fps with shadows. And when I disable them, it runs at 140+ fps !!

PS: All other settings in the graphic menu have way less performances impact than shadows.
Oh, and if I spawn more than one traffic car, my fps drops down to 60 again.