Keep items in arbitraryDataFileHashResponses if they are currently being requested by another thread. This should help to locate the higher numbered chunks from larger resources.

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

@@ -37,7 +37,7 @@ public class ArbitraryDataFileManager extends Thread {
     /**
      * Map to keep track of our in progress (outgoing) arbitrary data file requests
      */
-    private Map<String, Long> arbitraryDataFileRequests = Collections.synchronizedMap(new HashMap<>());
+    public Map<String, Long> arbitraryDataFileRequests = Collections.synchronizedMap(new HashMap<>());
 
     /**
      * Map to keep track of hashes that we might need to relay
@@ -148,7 +148,7 @@ public class ArbitraryDataFileManager extends Thread {
                     }
                 }
                 else {
-                    LOGGER.trace("Already requesting data file {} for signature {}", arbitraryDataFile, Base58.encode(signature));
+                    LOGGER.trace("Already requesting data file {} for signature {} from peer {}", arbitraryDataFile, Base58.encode(signature), peer);
                 }
             }
             else {

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

@@ -80,6 +80,12 @@ public class ArbitraryDataFileRequestThread implements Runnable {
                     continue;
                 }
 
+                // Skip if already requesting, but don't remove, as we might want to retry later
+                if (arbitraryDataFileManager.arbitraryDataFileRequests.containsKey(hash58)) {
+                    // Already requesting - leave this attempt for later
+                    continue;
+                }
+
                 // We want to process this file
                 shouldProcess = true;
                 iterator.remove();