added synchronization to WindTrackImpl.add again since it seems not to have been at fault; added threads:

One thread per listener in the UDPReceiver. They each have a bounded queue and wait for incoming
messages with a timeout. They are stopped when the listener unsubscribes.

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/WindTrackImpl.java

@@ -63,7 +63,9 @@ public class WindTrackImpl extends TrackImpl<Wind> implements WindTrack {
 
     @Override
     public void add(Wind wind) {
-        getInternalRawFixes().add(wind);
+        synchronized (this) {
+            getInternalRawFixes().add(wind);
+        }
         notifyListenersAboutReceive(wind);
     }