ValueTreeSynchroniser connect to GUI

I’m syncing 2 ValueTrees with ValueTreeSynchroniser between two applications.

In both apps a slider is attached to the ValueTree using slider.getValueObject.referTo ()
This happens of course before the ValueTrees are synced, however the ValueTrees are generated by the same method, so their structure is identical.

Now when moving the slider in App A its value is mirrored to the Slider in App B, however when moving the slider in App B only App A’s ValueTree changes, the Slider doesn’t move.

I suspect the ValueTreeSynchroniser somehow messes with the underlying values.

How would I solve this?

EDIT: sendFullSyncCallback() seems to be the problem, as it causes the valuetree to be overwritten, probably breaking the references.