@Peter Boese
when I have a normal session, I see Running Update takes up around 0.2 ms
View attachment 1474426
on a "bad" session, it takes around 1.3 ms :
View attachment 1474427
But is it cause or effect ?

(hoping you are onto something ...)
BTW , this was taken while not using Pure and without using a PP filter...
View attachment 1474428
Thanks already for your input and your everlasting efforts!
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@shi
Something entirely unrelated, ( I would like to put this in a separate post ,but that's against the rules)
How to fix the position of a floating groove?
View attachment 1474410View attachment 1474409
would this be feasible for me to change with code in extension\ext_config.ini or would it take some work in Blender (then I can't do this myself unfortunately)
Since Bikernieki High Speed is my #1 go-to track for testing cars, I would love to see those grooves fixed (they are all floating above the tarmac now...