diff --git a/OpenRa.Game/PathFinder.cs b/OpenRa.Game/PathFinder.cs
index 3cbd755102..c5a211e0df 100644
--- a/OpenRa.Game/PathFinder.cs
+++ b/OpenRa.Game/PathFinder.cs
@@ -54,7 +54,7 @@ namespace OpenRa.Game
 			for( int i = 0 ; i < path.Count ; i++ )
 			{
 				var sl = path[ i ] + offset;
-				if( Game.BuildingInfluence.GetBuildingAt( path[ i ] ) == null & Game.UnitInfluence.GetUnitAt( path[ i ] ) == null )
+				if( i == 0 || Game.BuildingInfluence.GetBuildingAt( path[ i ] ) == null & Game.UnitInfluence.GetUnitAt( path[ i ] ) == null )
 				{
 					queue.Add( new PathDistance( estimator( sl - offset ), sl ) );
 					cellInfo[ sl.X, sl.Y ] = new CellInfo( cost, prev, false );
diff --git a/OpenRa.Game/Traits/Mobile.cs b/OpenRa.Game/Traits/Mobile.cs
index 2746fb115f..e2f9a0f4fc 100644
--- a/OpenRa.Game/Traits/Mobile.cs
+++ b/OpenRa.Game/Traits/Mobile.cs
@@ -21,7 +21,8 @@ namespace OpenRa.Game.Traits
 		public Mobile(Actor self)
 		{
 			this.self = self;
-			fromCell = toCell;
+			fromCell = toCell;
+			Game.UnitInfluence.Update( this );
 		}
 
 		public void QueueActivity( CurrentActivity nextActivity )
@@ -205,7 +206,7 @@ namespace OpenRa.Game.Traits
 				var nextCell = path[ path.Count - 1 ];
 				if( !CanEnterCell( nextCell, self ) )
 				{
-					if( ( mobile.toCell - destination.Value ).LengthSquared < 4 )
+					if( ( mobile.toCell - destination.Value ).LengthSquared <= 8 )
 					{
 						path.Clear();
 						return null;
diff --git a/OpenRa.Game/UiOverlay.cs b/OpenRa.Game/UiOverlay.cs
index cdb6f784ed..c1e12c2b83 100644
--- a/OpenRa.Game/UiOverlay.cs
+++ b/OpenRa.Game/UiOverlay.cs
@@ -1,7 +1,7 @@
 using System.Drawing;
 using OpenRa.Game.Graphics;
 using System;
-using OpenRa.Game.GameRules;
+using OpenRa.Game.GameRules;
 using System.Linq;
 
 namespace OpenRa.Game
@@ -9,8 +9,8 @@ namespace OpenRa.Game
 	class UiOverlay
 	{
 		SpriteRenderer spriteRenderer;
-		Sprite buildOk, buildBlocked, unitDebug;
-
+		Sprite buildOk, buildBlocked, unitDebug;
+
 		public static bool ShowUnitDebug = false;
 
 		public UiOverlay(SpriteRenderer spriteRenderer)
@@ -18,7 +18,7 @@ namespace OpenRa.Game
 			this.spriteRenderer = spriteRenderer;
 
 			buildOk = SynthesizeTile(0x80);
-			buildBlocked = SynthesizeTile(0xe6);
+			buildBlocked = SynthesizeTile(0xe6);
 			unitDebug = SynthesizeTile(0x7c);
 		}
 
@@ -34,22 +34,22 @@ namespace OpenRa.Game
 		}
 
 		public void Draw()
-		{
-			if (ShowUnitDebug)
-				for (var j = 0; j < 128; j++)
-					for (var i = 0; i < 128; i++)
-						if (Game.UnitInfluence.GetUnitAt(new int2(i, j)) != null)
+		{
+			if (ShowUnitDebug)
+				for (var j = 0; j < 128; j++)
+					for (var i = 0; i < 128; i++)
+						if (Game.UnitInfluence.GetUnitAt(new int2(i, j)) != null)
 							spriteRenderer.DrawSprite(unitDebug, Game.CellSize * new float2(i, j), 0);
 
-			if (!hasOverlay) return;
-
-			var bi = (UnitInfo.BuildingInfo)Rules.UnitInfo[name];
-			
-			var maxDistance = bi.Adjacent + 2;	/* real-ra is weird. this is 1 GAP. */
-			var tooFarFromBase = !Footprint.Tiles(bi, position).Any(
-				t => Game.GetDistanceToBase(t, Game.LocalPlayer) < maxDistance);
-
-			foreach( var t in Footprint.Tiles( bi, position ) )
+			if (!hasOverlay) return;
+
+			var bi = (UnitInfo.BuildingInfo)Rules.UnitInfo[name];
+			
+			var maxDistance = bi.Adjacent + 2;	/* real-ra is weird. this is 1 GAP. */
+			var tooFarFromBase = !Footprint.Tiles(bi, position).Any(
+				t => Game.GetDistanceToBase(t, Game.LocalPlayer) < maxDistance);
+
+			foreach( var t in Footprint.Tiles( bi, position ) )
 				spriteRenderer.DrawSprite( !tooFarFromBase && Game.IsCellBuildable( t, bi.WaterBound 
 					? UnitMovementType.Float : UnitMovementType.Wheel )
 					? buildOk : buildBlocked, Game.CellSize * t, 0 );
diff --git a/OpenRa.Game/UnitInfluenceMap.cs b/OpenRa.Game/UnitInfluenceMap.cs
index 16ffe011fe..86788ec8d1 100644
--- a/OpenRa.Game/UnitInfluenceMap.cs
+++ b/OpenRa.Game/UnitInfluenceMap.cs
@@ -18,19 +18,38 @@ namespace OpenRa.Game
 
 		public void Tick()
 		{
+			SanityCheck();
+
 			var units = Game.world.Actors
 				.Select( a => a.traits.GetOrDefault<Traits.Mobile>() ).Where( m => m != null );
 
 			foreach (var u in units)
 				Update(u);
+
+			SanityCheck();
+		}
+
+		[System.Diagnostics.Conditional( "SANITY_CHECKS" )]
+		void SanityCheck()
+		{
+			for( int y = 0 ; y < 128 ; y++ )
+				for( int x = 0 ; x < 128 ; x++ )
+					if( influence[ x, y ] != null && !influence[ x, y ].traits.Get<Mobile>().OccupiedCells().Contains( new int2( x, y ) ) )
+						throw new InvalidOperationException( "UIM: Sanity check failed A" );
+
+			foreach( var a in Game.world.Actors )
+			{
+				if( !a.traits.Contains<Mobile>() )
+					continue;
+				foreach( var cell in a.traits.Get<Mobile>().OccupiedCells() )
+					if( influence[ cell.X, cell.Y ] != a )
+						throw new InvalidOperationException( "UIM: Sanity check failed B" );
+			}
 		}
 
 		public Actor GetUnitAt( int2 a )
 		{
-			var actor = influence[ a.X, a.Y ];
-			if( actor != null && !actor.traits.Get<Mobile>().OccupiedCells().Contains( a ) )
-				throw new InvalidOperationException( "UIM: Unit is not in influenced square" );
-			return actor;
+			return influence[ a.X, a.Y ];
 		}
 
 		public void Add(Mobile a)