XPS 17 9700 GPU Heavy Peaking / Dropping since newest drivers

XPS17 9700 i7 10875 with RTX 2060

since the last official driver updates I have heavy performance drops in plying CSGO and rendering. 
i am running in Ultra Performance Mode (Dell Thermal Management Tool)

it is not throtteling the GPU Performance but heavily dropping down to 10% power e.g. in CSGO Frames per second drop from 240 to 35. this lasts for some seconds only (5-10s) and then goes back to full power. The behavior repeats regularly every some minutes. 

this not a normal throttling behavior and looks Buggy to me.

this problem is NEW since last driver updates by Dell. I never had this issue before and start regretting doing Dells updates. System was good out of the box.

any experience or advice?