diff --git a/Subsurface/Source/Map/Submarine.cs b/Subsurface/Source/Map/Submarine.cs
index 82a9e03f7..43082e032 100644
--- a/Subsurface/Source/Map/Submarine.cs
+++ b/Subsurface/Source/Map/Submarine.cs
@@ -612,7 +612,11 @@ namespace Barotrauma
             
             subBody.Update(deltaTime);
 
-            if (this != MainSub && MainSub.DockedTo.Contains(this)) return;
+            for (int i = 0; i < 2; i++ )
+            {
+                if (Submarine.MainSubs[i] == null) continue;
+                if (this != Submarine.MainSubs[i] && Submarine.MainSubs[i].DockedTo.Contains(this)) return;
+            }
 
             //send updates more frequently if moving fast
             networkUpdateTimer -= MathHelper.Clamp(Velocity.Length()*10.0f, 0.1f, 5.0f) * deltaTime;
diff --git a/Subsurface/Source/Physics/PhysicsBody.cs b/Subsurface/Source/Physics/PhysicsBody.cs
index f528d4af9..48d43589f 100644
--- a/Subsurface/Source/Physics/PhysicsBody.cs
+++ b/Subsurface/Source/Physics/PhysicsBody.cs
@@ -331,6 +331,11 @@ namespace Barotrauma
 
         public void SetTransform(Vector2 position, float rotation)
         {
+            System.Diagnostics.Debug.Assert(MathUtils.IsValid(position));
+            System.Diagnostics.Debug.Assert(Math.Abs(position.X) < 1000000.0f);
+            System.Diagnostics.Debug.Assert(Math.Abs(position.Y) < 1000000.0f);
+            
+
             body.SetTransform(position, rotation);
             SetPrevTransform(position, rotation);
         }