ARMapRenderer: Do not null-set relay because we are no longer looping. Bail out and log whenever target relays or their vessels are null and the target relay isn't KerbinDirect.
ARMapRenderer: Do not null-set relay because we are no longer looping. Bail out and log whenever target relays or their vessels are null and the target relay isn't KerbinDirect.

--- a/ARMapRenderer.cs
+++ b/ARMapRenderer.cs
@@ -167,6 +167,7 @@
 
 						if (vesselRelay == null)
 						{
+							log.AppendFormat("\n\tGot null relay for vessel {0}", vessel.vesselName);
 							continue;
 						}
 
@@ -206,7 +207,7 @@
 		{
 			this.Cleanup();
 
-			print("ARMapRenderer: Destroyed.");
+			this.Log("Destroyed");
 		}
 		#endregion
 
@@ -273,18 +274,21 @@
 			if (relay.KerbinDirect)
 			{
 				nextPoint = ScaledSpace.LocalToScaledSpace(AntennaRelay.Kerbin.position);
-				relay = null;
 			}
 			else
 			{
-				if (relay.targetRelay == null)
-				{
+				if (relay.targetRelay == null || relay.targetRelay.vessel == null)
+				{
+					this.LogError(
+						"SetRelayVertices: relay {0} has null target relay or vessel when not KerbinDirect, bailing out!",
+						relay
+					);
+
 					renderer.enabled = false;
 					return;
 				}
 
 				nextPoint = ScaledSpace.LocalToScaledSpace(relay.targetRelay.vessel.GetWorldPos3D());
-				relay = relay.targetRelay;
 			}
 
 			renderer.SetColors(thisColor, thisColor);

--- a/AntennaRelay.cs
+++ b/AntennaRelay.cs
@@ -221,6 +221,7 @@
 				
 				if (potentialVessel == null)
 				{
+					Tools.PostErrorMessage("{0}: Skipping vessel at index {1} because it is null.", this, vIdx);
 					log.AppendFormat("\n\tSkipping vessel at index {0} because it is null.", vIdx);
 					log.Print();
 					return;

--- a/RelayDatabase.cs
+++ b/RelayDatabase.cs
@@ -72,9 +72,6 @@
 		// Vessel.id-keyed hash table of part counts, used for caching
 		private Dictionary<Guid, int> vesselPartCountTable;
 
-		// Vessel.id-keyed hash table of booleans to track what vessels have been checked so far this time.
-		public Dictionary<Guid, bool> CheckedVesselsTable;
-
 		private int cacheHits;
 		private int cacheMisses;
 
@@ -117,9 +114,16 @@
 		// Remove a vessel from the cache, if it exists.
 		public void DirtyVessel(Vessel vessel)
 		{
+			#if DEBUG
+			Tools.PostDebugMessage("RelayDatabase: Dirtying cache for vessel {0} in frame {1}",
+				vessel, new System.Diagnostics.StackTrace().ToString());
+			#else
+			Tools.PostLogMessage("RelayDatabase: Dirtying cache for vessel {0}", vessel.vesselName);
+			#endif
+
 			this.relayDatabase.Remove(vessel.id);
 			this.vesselPartCountTable.Remove(vessel.id);
-			this.relayDatabase.Remove(vessel.id);
+			this.bestRelayTable.Remove(vessel.id);
 		}
 
 		// Returns true if both the relayDatabase and the vesselPartCountDB contain the vessel id.
@@ -228,11 +232,33 @@
 		// Runs when the player requests a scene change, such as when changing vessels or leaving flight.
 		private void onSceneChange(GameScenes scene)
 		{
-			// If the active vessel is a real thing...
-			if (FlightGlobals.ActiveVessel != null)
-			{
-				// ... dirty its cache
-				this.onVesselEvent(FlightGlobals.ActiveVessel);
+			Tools.PostDebugMessage(
+				"RelayDatabase: caught onSceneChangeRequested in scene {0} to scene {1}.  ActiveVessel is {2}",
+				HighLogic.LoadedScene,
+				scene,
+				FlightGlobals.ActiveVessel == null ? "null" : FlightGlobals.ActiveVessel.vesselName
+			);
+
+			if (scene == GameScenes.FLIGHT)
+			{
+				if (scene == HighLogic.LoadedScene)
+				{
+					if (FlightGlobals.ActiveVessel != null)
+					{
+						Tools.PostDebugMessage("RelayDatabase: onSceneChange clearing {0} from cache.",
+							FlightGlobals.ActiveVessel.vesselName);
+
+						this.onVesselEvent(FlightGlobals.ActiveVessel);
+					}
+				}
+				else
+				{
+					Tools.PostLogMessage("RelayDatabase: onSceneChange clearing entire cache.");
+
+					this.relayDatabase.Clear();
+					this.bestRelayTable.Clear();
+					this.vesselPartCountTable.Clear();
+				}
 			}
 		}
 
@@ -394,7 +420,6 @@
 			this.relayDatabase = new Dictionary<Guid, List<IAntennaRelay>>();
 			this.bestRelayTable = new Dictionary<Guid, IAntennaRelay>();
 			this.vesselPartCountTable = new Dictionary<Guid, int>();
-			this.CheckedVesselsTable = new Dictionary<Guid, bool>();
 
 			this.cacheHits = 0;
 			this.cacheMisses = 0;