Synchronize arbitrary data list removals, as it seems that SynchronizedList and SynchronizedMap aren't overriding removeIf() with a thread-safe version.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataBuildManager.java

@@ -75,9 +75,13 @@ public class ArbitraryDataBuildManager extends Thread {
         if (now == null) {
             return;
         }
+        synchronized (arbitraryDataBuildQueue) {
             arbitraryDataBuildQueue.entrySet().removeIf(entry -> entry.getValue().hasReachedBuildTimeout(now));
+        }
+        synchronized (arbitraryDataFailedBuilds) {
             arbitraryDataFailedBuilds.entrySet().removeIf(entry -> entry.getValue().hasReachedFailureTimeout(now));
         }
+    }
 
     // Build queue
 

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileListManager.java

@@ -84,8 +84,10 @@ public class ArbitraryDataFileListManager {
             return;
         }
         final long requestMinimumTimestamp = now - ArbitraryDataManager.ARBITRARY_REQUEST_TIMEOUT;
+        synchronized (arbitraryDataFileListRequests) {
             arbitraryDataFileListRequests.entrySet().removeIf(entry -> entry.getValue().getC() == null || entry.getValue().getC() < requestMinimumTimestamp);
         }
+    }
 
 
     // Track file list lookups by signature

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileManager.java

@@ -101,15 +101,23 @@ public class ArbitraryDataFileManager extends Thread {
             return;
         }
         final long requestMinimumTimestamp = now - ArbitraryDataManager.getInstance().ARBITRARY_REQUEST_TIMEOUT;
+        synchronized (arbitraryDataFileRequests) {
             arbitraryDataFileRequests.entrySet().removeIf(entry -> entry.getValue() == null || entry.getValue() < requestMinimumTimestamp);
+        }
 
         final long relayMinimumTimestamp = now - ArbitraryDataManager.getInstance().ARBITRARY_RELAY_TIMEOUT;
+        synchronized (arbitraryRelayMap) {
             arbitraryRelayMap.removeIf(entry -> entry == null || entry.getTimestamp() == null || entry.getTimestamp() < relayMinimumTimestamp);
+        }
+        synchronized (arbitraryDataFileHashResponses) {
             arbitraryDataFileHashResponses.removeIf(entry -> entry.getTimestamp() < relayMinimumTimestamp);
+        }
 
         final long directConnectionInfoMinimumTimestamp = now - ArbitraryDataManager.getInstance().ARBITRARY_DIRECT_CONNECTION_INFO_TIMEOUT;
+        synchronized (directConnectionInfo) {
             directConnectionInfo.removeIf(entry -> entry.getTimestamp() < directConnectionInfoMinimumTimestamp);
         }
+    }
 
 
 
@@ -484,8 +492,10 @@ public class ArbitraryDataFileManager extends Thread {
     }
 
     private void removeFromRelayMap(ArbitraryRelayInfo entry) {
+        synchronized (arbitraryRelayMap) {
             arbitraryRelayMap.removeIf(relayInfo -> relayInfo.equals(entry));
         }
+    }
 
 
     // Network handlers

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataRenderManager.java

@@ -56,8 +56,10 @@ public class ArbitraryDataRenderManager extends Thread {
             return;
         }
         final long minimumTimestamp = now - AUTHORIZATION_TIMEOUT;
+        synchronized (this.authorizedResources) {
             this.authorizedResources.entrySet().removeIf(entry -> entry.getValue() == null || entry.getValue() < minimumTimestamp);
         }
+    }
 
     public boolean isAuthorized(ArbitraryDataResource resource) {
         ArbitraryDataResource broadResource = new ArbitraryDataResource(resource.getResourceId(), null, null, null);

src/main/java/org/qortal/controller/arbitrary/ArbitraryMetadataManager.java

@@ -73,8 +73,10 @@ public class ArbitraryMetadataManager {
             return;
         }
         final long requestMinimumTimestamp = now - ArbitraryDataManager.ARBITRARY_REQUEST_TIMEOUT;
+        synchronized (arbitraryMetadataRequests) {
             arbitraryMetadataRequests.entrySet().removeIf(entry -> entry.getValue().getC() == null || entry.getValue().getC() < requestMinimumTimestamp);
         }
+    }
 
 
     public ArbitraryDataTransactionMetadata fetchMetadata(ArbitraryDataResource arbitraryDataResource, boolean useRateLimiter) {