Server Exception on transformation precondition about swellrt HOT 1 CLOSED

@Override
  public void appendDelta(WaveletDeltaRecord deltaRecord)
      throws OperationException {
    HashedVersion currentVersion = getCurrentVersion();
    Preconditions.checkArgument(currentVersion.equals(deltaRecord.getAppliedAtVersion()),
        "Applied version %s doesn't match current version %s", deltaRecord.getAppliedAtVersion(),
        currentVersion);



      if (deltaRecord.getAppliedAtVersion().getVersion() == 0) {
        Preconditions.checkState(lastPersistedVersion.get() == null);
        snapshot = WaveletDataUtil.buildWaveletFromFirstDelta(getWaveletName(), deltaRecord.getTransformedDelta());
        contributions = new WaveletContributions(deltasAccess.getWaveletName());
        contributions.apply(deltaRecord.getTransformedDelta());
      } else {
        // Avoid to update snapshot when it has being persisted
        synchronized (persistLock) {
          WaveletDataUtil.applyWaveletDelta(deltaRecord.getTransformedDelta(), snapshot);
          contributions.apply(deltaRecord.getTransformedDelta());
        }
      }


    // Now that we built the snapshot without any exceptions, we record the delta.
    cachedDeltas.put(deltaRecord.getAppliedAtVersion(), deltaRecord); <------- UNSAFE UPDATE

    // Increment counter controlling snapshot persistence
    deltasCountBeforeSnapshotStore++;
  }