Solved

Health depletion rate

Unfair advantage using softer tyres.

Supersoft push level 2 loss 0.1 per lap
Soft push level 2 loss 0.1 per lap
Meduim push level 2 loss 0.7 per lap
Hard push level 2 loss 0.7 per lap

Just encase your thinking it cant be possible & how would I know lol
Race results show I used all 4 compounds https://igpmanager.com/app/d=resultDetail&id=3514441

I see a flaw in your method. Reverse the order of tire usage and see if it's the 2nd half of the race or the compund

start of the race i was on the highest push level for nearly the full stint and it was still 0.1

Was going super tonight up until lap 42 of 60. https://igpmanager.com/app/d=resultDetail&id=3527165

Start of the race 0.5 push level 1
2nd lap once tyres are up to temp drops to 0.4
Out-laps 0.5
once tyres are up to temp 0.4
push levels 1-3 = 0.4 all tyres
push levels 4 & 5 = 0.5 all tyres

once I hit lap 42 it all went to pot
push levels 1-4 = 0.0
push level 5 = 0.1

both drivers ended the race with 80% health