I found the solution for this bug after many races (in 100% distance) in a GP4 multiplayer championship...
To avoid the pit stop bug (mainly when have the option "fix pit stop bug" marked on GPxPatch) NEVER go the pit before the pitcrews say "go go go" when make a damage pit stop because the next pit all team will be waiting for you and anybody will work in the car.
You CAN go before the team say you to go when make a FUEL pit stop but NEVER when make a DAMAGE pit stop !
RICARDO LAMPERTVisit my blog at [ricardolampert.wordpress.com]