diff --git a/src/main/java/cr0s/warpdrive/data/ChunkData.java b/src/main/java/cr0s/warpdrive/data/ChunkData.java
index 0e4fb8ec..ab9284de 100644
--- a/src/main/java/cr0s/warpdrive/data/ChunkData.java
+++ b/src/main/java/cr0s/warpdrive/data/ChunkData.java
@@ -235,7 +235,11 @@ public class ChunkData {
 	
 	public void unload() {
 		// check consistency
-		assert(!isLoaded);
+		if (!isLoaded) {
+			WarpDrive.logger.warn(String.format("Chunk is already unloaded at (%d %d %d)",
+			                                    getChunkPosition().chunkPosX, getChunkPosition().chunkPosY, getChunkPosition().chunkPosZ));
+			return;
+		}
 		
 		// detects fast unloading
 		final long time = System.currentTimeMillis();
diff --git a/src/main/java/cr0s/warpdrive/data/EnumForceFieldUpgrade.java b/src/main/java/cr0s/warpdrive/data/EnumForceFieldUpgrade.java
index 5c1154c5..8b994a41 100644
--- a/src/main/java/cr0s/warpdrive/data/EnumForceFieldUpgrade.java
+++ b/src/main/java/cr0s/warpdrive/data/EnumForceFieldUpgrade.java
@@ -29,7 +29,7 @@ import net.minecraft.world.World;
 public enum EnumForceFieldUpgrade implements IForceFieldUpgrade, IForceFieldUpgradeEffector {
 	//            Upgrade         - Compatibility -  ----- Value -----  -- Scan speed --  -- Place speed --  --------- Energy costs ---------  comment
 	//            name            projector   relay    incr.       cap  minimum  maximum   minimum  maximum  startup   scan    place    entity  
-	NONE         ("none"         ,        0,      0,    0.0F,     0.0F,  0.000F,  0.000F,   0.000F,  0.000F,    0.0F, 0.000F,  0.000F,    0.0F, ""),
+	NONE         ("none"         ,        0,      0,    0.0F,     0.0F,  0.000F,  0.000F,   0.000F,  0.000F,    0.0F, 0.000F,  0.000F,    0.0F, "n/a"),
 	ATTRACTION   ("attraction"   ,        0,      1,    1.0F,     4.0F,  0.000F,  0.000F,   0.000F,  0.000F,   50.0F, 0.150F,  0.000F,    8.0F, "value is acceleration"),
 	BREAKING     ("breaking"     ,        0,      1,    1.0F,    25.0F,  0.400F,  0.500F,   0.020F,  0.150F,  700.0F, 0.080F,  4.000F,    0.0F, "value is hardness level"),
 	CAMOUFLAGE   ("camouflage"   ,        0,      1,    1.0F,     3.0F,  0.600F,  0.850F,   0.700F,  0.950F, 1000.0F, 3.000F,  7.000F,    0.0F, "value is boolean"),
diff --git a/src/main/java/cr0s/warpdrive/event/ChunkHandler.java b/src/main/java/cr0s/warpdrive/event/ChunkHandler.java
index 464d84e4..f6621409 100644
--- a/src/main/java/cr0s/warpdrive/event/ChunkHandler.java
+++ b/src/main/java/cr0s/warpdrive/event/ChunkHandler.java
@@ -26,7 +26,8 @@ import net.minecraftforge.event.world.WorldEvent;
 public class ChunkHandler {
 	
 	// persistent properties
-	private static final Map<Integer, Map<Long, ChunkData>> registry = new ConcurrentHashMap<>(32);
+	private static final Map<Integer, Map<Long, ChunkData>> registryClient = new ConcurrentHashMap<>(32);
+	private static final Map<Integer, Map<Long, ChunkData>> registryServer = new ConcurrentHashMap<>(32);
 	
 	// computed properties
 	public static long delayLogging = 0;
@@ -57,7 +58,7 @@ public class ChunkHandler {
 			                                    event.getChunk().getChunkCoordIntPair()));
 		}
 		
-		final ChunkData chunkData = getChunkData(event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
+		final ChunkData chunkData = getChunkData(event.world.isRemote, event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
 		chunkData.load(event.getData());
 	}
 	
@@ -71,7 +72,7 @@ public class ChunkHandler {
 				                                    event.getChunk().getChunkCoordIntPair()));
 			}
 			
-			final ChunkData chunkData = getChunkData(event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
+			final ChunkData chunkData = getChunkData(event.world.isRemote, event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
 			chunkData.load(new NBTTagCompound());
 		}
 	}
@@ -96,7 +97,7 @@ public class ChunkHandler {
 			                                    event.world.provider.getDimensionName(),
 			                                    event.getChunk().getChunkCoordIntPair()));
 		}
-		final ChunkData chunkData = getChunkData(event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
+		final ChunkData chunkData = getChunkData(event.world.isRemote, event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition);
 		chunkData.save(event.getData());
 	}
 	
@@ -126,6 +127,7 @@ public class ChunkHandler {
 		}
 		
 		// get dimension data
+		final Map<Integer, Map<Long, ChunkData>> registry = event.world.isRemote ? registryClient : registryServer;
 		final Map<Long, ChunkData> mapRegistryItems = registry.get(event.world.provider.dimensionId);
 		if (mapRegistryItems != null) {
 			// unload chunks during shutdown
@@ -153,7 +155,7 @@ public class ChunkHandler {
 			                                    event.getChunk().getChunkCoordIntPair()));
 		}
 		
-		getChunkData(event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition).unload();
+		getChunkData(event.world.isRemote, event.world.provider.dimensionId, event.getChunk().xPosition, event.getChunk().zPosition).unload();
 	}
 	
 	// (not called when closing SSP game)
@@ -183,16 +185,17 @@ public class ChunkHandler {
 	
 	/* internal access */
 	public static ChunkData getChunkData(final World world, final int x, final int y, final int z) {
-		return getChunkData(world.provider.dimensionId, x, y, z);
+		return getChunkData(world.isRemote, world.provider.dimensionId, x, y, z);
 	}
 	
-	private static ChunkData getChunkData(final int dimensionId, final int x, final int y, final int z) {
+	private static ChunkData getChunkData(final boolean isRemote, final int dimensionId, final int x, final int y, final int z) {
 		assert (y >= 0 && y <= 255);
-		return getChunkData(dimensionId, x >> 4, z >> 4);
+		return getChunkData(isRemote, dimensionId, x >> 4, z >> 4);
 	}
 	
-	private static ChunkData getChunkData(final int dimensionId, final int xChunk, final int zChunk) {
+	private static ChunkData getChunkData(final boolean isRemote, final int dimensionId, final int xChunk, final int zChunk) {
 		// get dimension data
+		final Map<Integer, Map<Long, ChunkData>> registry = isRemote ? registryClient : registryServer;
 		Map<Long, ChunkData> mapRegistryItems = registry.get(dimensionId);
 		// (lambda expressions are forcing synchronisation, so we don't use them here)
 		if (mapRegistryItems == null) {
@@ -229,6 +232,7 @@ public class ChunkHandler {
 	
 	public static void updateTick(final World world) {
 		// get dimension data
+		final Map<Integer, Map<Long, ChunkData>> registry = world.isRemote ? registryClient : registryServer;
 		Map<Long, ChunkData> mapRegistryItems = registry.get(world.provider.dimensionId);
 		if (mapRegistryItems == null) {
 			return;