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
@@ -26,8 +26,6 @@
 // WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#define DEBUG
-
 using System;
 using System.Collections.Generic;
 using ToadicusTools;
@@ -223,6 +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;
@@ -263,7 +262,7 @@
 				log.Append("\n\tgetting best vessel relay");
 
 				potentialBestRelay = potentialVessel.GetBestRelay();
-				log.AppendFormat("\n\tgot best vessel relay {0}",
+				log.AppendFormat("\n\t\tgot best vessel relay {0}",
 					potentialBestRelay == null ? "null" : potentialBestRelay.ToString());
 
 				if (potentialBestRelay == null)
@@ -272,25 +271,21 @@
 					continue;
 				}
 
-				// vesselRelays = potentialVessel.GetAntennaRelays();
-				/*	log.AppendFormat("\n\t\tvesselRelays: {0}",
-						vesselRelays == null ? "null" : vesselRelays.Count.ToString());*/
-				
-				log.Append("\n\tdoing LOS check");
+				log.Append("\n\t\tdoing LOS check");
 				// Skip vessels to which we do not have line of sight.
 				if (
 					ARConfiguration.RequireLineOfSight &&
 					!this.vessel.hasLineOfSightTo(potentialVessel, out fob, ARConfiguration.RadiusRatio)
 				)
 				{
-					log.Append("\n\tfailed LOS check");
-
-					log.AppendFormat("\n\t{0}: Vessel {1} not in line of sight.",
+					log.Append("\n\t\t...failed LOS check");
+
+					log.AppendFormat("\n\t\t\t{0}: Vessel {1} not in line of sight.",
 						this.ToString(), potentialVessel.vesselName);
 					
-					log.AppendFormat("\n\t\tpotentialSqrDistance: {0}", potentialSqrDistance);
-					log.AppendFormat("\n\t\tbestOccludedSqrDistance: {0}", bestOccludedSqrDistance);
-					log.AppendFormat("\n\t\tmaxTransmitSqrDistance: {0}", maxTransmitSqrDistance);
+					log.AppendFormat("\n\t\t\tpotentialSqrDistance: {0}", potentialSqrDistance);
+					log.AppendFormat("\n\t\t\tbestOccludedSqrDistance: {0}", bestOccludedSqrDistance);
+					log.AppendFormat("\n\t\t\tmaxTransmitSqrDistance: {0}", maxTransmitSqrDistance);
 
 					if (
 						(potentialSqrDistance < bestOccludedSqrDistance) &&
@@ -313,7 +308,7 @@
 					continue;
 				}
 
-				log.Append("\n\tpassed LOS check");
+				log.Append("\n\t\t...passed LOS check");
 
 				/*
 				 * ...so that we can skip the vessel if it is further away than a vessel we've already checked.
@@ -328,7 +323,7 @@
 					continue;
 				}
 
-				log.Append("\n\tpassed distance check");
+				log.Append("\n\t\t...passed distance check");
 
 				if (
 					potentialBestRelay.CanTransmit() &&
@@ -343,8 +338,6 @@
 						this.nearestRelay.ToString(),
 						Math.Sqrt(nearestRelaySqrDistance)
 					);
-					
-					break;
 				}
 			}
 

--- a/ModuleLimitedDataTransmitter.cs
+++ b/ModuleLimitedDataTransmitter.cs
@@ -145,13 +145,13 @@
 				{
 					return base.vessel;
 				}
-				else if (this.part != null)
+				else if (this.part != null && this.part.vessel != null)
 				{
 					return this.part.vessel;
 				}
-
 				else
 				{
+					this.LogError("Vessel and/or part reference are null, returning null vessel.");
 					return null;
 				}
 			}

--- a/ProtoAntennaRelay.cs
+++ b/ProtoAntennaRelay.cs
@@ -48,17 +48,24 @@
 		{
 			get
 			{
-				if (this.protoPart != null && this.protoPart.pVesselRef != null)
+				if (
+					this.protoPart != null &&
+					this.protoPart.pVesselRef != null &&
+					this.protoPart.pVesselRef.vesselRef != null
+				)
 				{
 					return this.protoPart.pVesselRef.vesselRef;
 				}
 				else
 				{
-					Tools.PostLogMessage("{0}: Could not fetch vessel!  {1}{2}{3}",
+					Tools.PostErrorMessage("{0}: Could not fetch vessel!  {1}{2}{3}",
 						this.ToString(),
-						this.protoPart == null ? "\n\tprotoPart=Null" : string.Empty,
-						this.protoPart != null && this.protoPart.pVesselRef == null ? "\n\tthis.protoPart.pVesselRef=Null" : string.Empty,
-						this.protoPart != null && this.protoPart.pVesselRef != null && this.protoPart.pVesselRef.vesselRef == null ? "\n\tthis.protoPart.pVesselRef.vesselRef=Null" : string.Empty
+						this.protoPart == null ? "\n\tprotoPart=null" : string.Empty,
+						this.protoPart != null && this.protoPart.pVesselRef == null ?
+							"\n\tthis.protoPart.pVesselRef=null" : string.Empty,
+						this.protoPart != null && this.protoPart.pVesselRef != null &&
+							this.protoPart.pVesselRef.vesselRef == null ?
+							"\n\tthis.protoPart.pVesselRef.vesselRef=null" : string.Empty
 					);
 					return null;
 				}

--- 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;