i have big problem collision? handling? and missing part need help

[Deathcode studio]

hi i have problem with my cars.. every car is too light when crash with other cars just fly high I tried set mass in handling and copy other handling but no effects...
What else can I do? or this is colision in model?

and i have 2 bug my window in door missing i tried add new and this same situations

https://imgur.com/a/gDJCs screens

please help

[alex20121981]

You have the problem just with addon cars..?

[Deathcode studio]

@alex20121981 No addon version i create when i fix this bug:) this is the same bug TRANS AM from baba0rum https://www.gta5-mods.com/vehicles/pontiac-trans-am-1977 but he fix this

[alex20121981]

go here
C:\Users\User\Documents\Rockstar Games\GTA V

and open in launcher.log file, look for
ERROR (HRESULT)

If you have it, post launcher.log file here...