Strange shadow tri wobble degrading performance

Hello, I ran into a very strange question for myself, hoping to get an answer from you who understand this.
Generally noticed that the shadow tri increases dramatically in inexplicable situations, spoiling performance.
The video below shows that the initial number of shadow triangles fluctuates between 2-3 million, but then for some reason it increases to 7 million, to 6, and then drops sharply to 3
this situation is related to the car and I use future lighting