Hammer crashes when adding any prop_vehicle

[Grillet]

When I add a prop_vehicle or any of the other, like prop_vehicle_jeep, Hammer instantly crashes. Adding other entities works just fine.

I tried to add a prop_vehicle entity using hammer.exe in the /bin folder where Gmod is installed and it worked. I then tried to open that map with Hammer that is setup with Source Multi-Tool and Hammer crashes and creates a .mdmp file.

I've setup Hammer with Source Multi-Tool with GarrysMod content and the following FGD's: base.fgd, garrysmod.fgd, halflife2.fgd and sdk.fdg.
Any help is welcome.