Clip only spawning on servers


So I’ve made 2 vehicle mods now and after installing them on servers I noticed only the clip spawns.
I have tried on several Pcs on singleplayer and the mods work. What am I doing wrong?

This is what the console shows:
2 mods, wich add vehicles, and they work fine on a machine that didn’t have them before I uploaded them, so I know they work in singleplayer. However, when I install them on my server, this pops up in the console:

An error occured while executing v [2704]: System.NullReferenceException: Object reference not set to an instance of an object
at SDG.Unturned.InteractableVehicle.init () [0x00000] in :0
at SDG.Unturned.VehicleManager.addVehicle (UInt16 id, UInt16 skinID, UInt16 mythicID, Single roadPosition, Vector3 point, Quaternion angle, Boolean sirens, Boolean blimp, Boolean headlights, Boolean taillights, UInt16 fuel, Boolean isExploded, UInt16 health, UInt16 batteryCharge, CSteamID owner, CSteamID group, Boolean locked, Steamworks.CSteamID[] passengers, System.Byte[][] turrets, UInt32 instanceID, Byte tireAliveMask) [0x00000] in :0
at SDG.Unturned.VehicleManager.spawnVehicle (UInt16 id, Vector3 point, Quaternion angle) [0x00000] in :0
at SDG.Unturned.VehicleTool.giveVehicle (SDG.Unturned.Player player, UInt16 id) [0x00000] in :0
at Rocket.Unturned.Commands.CommandV.Execute (IRocketPlayer caller, System.String[] command) [0x00000] in :0
at Rocket.Core.Commands.RocketCommandManager+RegisteredRocketCommand.Execute (IRocketPlayer caller, System.String[] command) [0x00000] in :0
at Rocket.Core.Commands.RocketCommandManager.Execute (IRocketPlayer player, System.String command) [0x00000] in : 100: Thanks for reading!