Crash when shoot at cars

Hello, I would like some help with my gmod. As you can see by the title, when I or anyone else shoots a car [LW] theirs and many around them game crashes. Now, i would just use TDM but their cars are no where near as good as LW so if you can help then please please do

Thanks

Reduce your decals on models convar to 0

Can I do this for the whole server? Also how do I do this sorry, im a noob with stuff like this