My game get's slower overtime

When i first load up a map it loads fast and the vehicle selection menu also loads fast. But after about 3-5 resets of the car, or messing with the part editor the game start's to lag and the vehicle selection menu loads in about 30-40 seconds (usually for me it takes about 5 seconds). Sometimes the frames also drop. Is there any way to fix this (yes I've deactivated all my mods).

 

if not that you might need to clear cache before starting the game