Formula Reiza - big difference in pit stop times - define fixed value?


i like to do 10 lap races with the formula reiza cars but i have a problem with the pit stop times. i modified the track files that every car is going to do a pitstop in this 10 laps. that's working great so far. but i saw a strange behaviour when i recognized the pit stop times of each car. in most cases the pit stops last about 4 to 5 seconds. but sometimes, a pit stop lasts about 15 to 20 seconds?? i have no idea why some cars need more than 10 seconds longer to do their stop. there is no reason for such a behaviour because i turned everything off which might result in longer pitstop times. invulnerability is on, damage multiplier 0%, mechanical failures off (even this two options should make no difference because of invulnerability).

did someone recognized the same behaviour? is there a possibility to define a fixed value for the pit stop duration in certain config files?