It should be opposite. Using the hardest (hard/medium) compound available during sprint race, with zero pitstops. That fixes all tyre allocation bugs.
If you do a 1 pitstop and use two tyres, the feature race becomes bugged.
So to fix this is very simple. Simply manually edit the sprint race strategy that has medium/hard in it. And remove the soft or supersoft. And the f2 career game is fixed. no more bugs.
on long runs 50% you say ? because in the long races the main strategy in sprint is already a hard/medium, and I don't stop in the sprint, I go to the end with a set of tires. in the average races of 35% the main strategy is to use soft tires in the sprint with 0 stops, this strategy is the same for the AI and if I set it to go with hard/medium in the sprint the AI will go soft.
