This is just part of the log but I noticed it happening with a random generated spawned atmo ship.

018-11-18 17:44:43.186 - Thread: 1 -> Modular Encounters Spawner: Attempting Planetary Cargo Ship Spawn Near Player: requiemfang
2018-11-18 17:44:43.547 - Thread: 1 -> Modular Encounters Spawner: Spawning Group - (Atmo)(NPC-ATM) Mobile Drilling Platform
2018-11-18 17:44:44.953 - Thread: 1 -> GC Memory: 3,596,819,376 B
2018-11-18 17:44:47.694 - Thread: 1 -> Exception occured: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at System.ThrowHelper.ThrowKeyNotFoundException()
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
at SpaceEngineers.Game.Weapons.Guns.MyLargeInteriorTurret.OnModelChange()
at Sandbox.Game.Entities.MyCubeBlock.Init()
at Sandbox.Game.Entities.MyCubeBlock.Init(MyObjectBuilder_CubeBlock builder, MyCubeGrid cubeGrid)
at Sandbox.Game.Entities.Cube.MyTerminalBlock.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid)
at Sandbox.Game.Entities.Cube.MyFunctionalBlock.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid)
at Sandbox.Game.Weapons.MyUserControllableGun.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid)
at Sandbox.Game.Weapons.MyLargeTurretBase.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid)
at SpaceEngineers.Game.Weapons.Guns.MyLargeInteriorTurret.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid)
at Sandbox.Game.Entities.Cube.MySlimBlock.Init(MyObjectBuilder_CubeBlock objectBuilder, MyCubeGrid cubeGrid, MyCubeBlock fatBlock)
at Sandbox.Game.Entities.MyCubeGrid.AddCubeBlock(MyObjectBuilder_CubeBlock objectBuilder, Boolean testMerge, MyCubeBlockDefinition blockDefinition)
at Sandbox.Game.Entities.MyCubeGrid.AddBlock(MyObjectBuilder_CubeBlock objectBuilder, Boolean testMerge)
at Sandbox.Game.Entities.MyCubeGrid.BuildBlock(MyCubeBlockDefinition blockDefinition, Vector3 colorMaskHsv, Vector3I min, Quaternion orientation, Int64 owner, Int64 entityId, MyEntity builderEntity, MyObjectBuilder_CubeBlock blockObjectBuilder, Boolean updateVolume, Boolean testMerge, Boolean buildAsAdmin)
at Sandbox.Game.Entities.MyCubeGrid.BuildBlocksSuccess(Vector3 colorMaskHsv, HashSet`1 locations, HashSet`1 resultBlocks, MyEntity builder, Boolean instantBuilt, Int64 ownerId)
at Sandbox.Game.Entities.MyCubeGrid.BuildBlocksRequest(UInt32 colorMaskHsv, HashSet`1 locations, Int64 builderEntityId, Boolean instantBuild, Int64 ownerId)
at VRage.Network.MyReplicationLayerBase.InvokeLocally[T1,T2,T3,T4,T5,T6,T7](CallSite`7 site, T1 arg1, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, T7 arg7)
at VRage.Network.MyReplicationSingle.DispatchEvent[T1,T2,T3,T4,T5,T6,T7,T8](CallSite callSite, EndpointId recipient, Nullable`1 position, T1& arg1, T2& arg2, T3& arg3, T4& arg4, T5& arg5, T6& arg6, T7& arg7, T8& arg8)
at VRage.Network.MyReplicationLayerBase.RaiseEvent[T1,T2,T3,T4,T5,T6,T7](T1 arg1, T7 arg7, Func`2 action, T2 arg2, T3 arg3, T4 arg4, T5 arg5, T6 arg6, EndpointId endpointId, Nullable`1 position)
at Sandbox.Game.Entities.MyCubeGrid.BuildBlocks(Vector3 colorMaskHsv, HashSet`1 locations, Int64 builderEntityId, Int64 ownerId)
at NPCWeaponUpgrades.NWU_SessionCore.ProcessGrid(IMyCubeGrid cubeGrid)
at NPCWeaponUpgrades.NWU_SessionCore.UpdateBeforeSimulation()
at Sandbox.Game.World.MySession.UpdateComponents()
at Sandbox.Game.World.MySession.Update(MyTimeSpan updateTime)
at Sandbox.MySandboxGame.Update()
at Sandbox.Engine.Platform.Game.UpdateInternal()
at Sandbox.Engine.Platform.Game.RunSingleFrame()
at Sandbox.Engine.Platform.FixedLoop.<>c__DisplayClass1.<Run>b__0()
at Sandbox.Engine.Platform.GenericLoop.Run(VoidAction tickCallback)
at Sandbox.Engine.Platform.Game.RunLoop()
at Sandbox.MySandboxGame.Run(Boolean customRenderLoop, Action disposeSplashScreen)
at SpaceEngineers.MyProgram.Main(String[] args)