Synchronisation suspended between Partitur and Part

Under some unknown circumstances syncronisation ist stopped (suspended) between Partitur and Part. Notes and Measures can be inserted and deleted. Existig notes will not be synchronized if changed in either Partitur or Part (Keys, Articulation, Slurs, etc.). Changes are suspended in in both directions. It can be reestablished only when the part is resetted. But from this moment all particular formatting of the part is also lost.
Is this a known problem? I could not find some ticket?