I've had several issues with the FMS enroute while modifying the FP - either inserting a direct to or adding an Arrival prior to descent.  In both cases my existing FP was deleted and no way to recover it.  End of flight....guess you can't touch the FP after initial setup. 

After this happened the last time I attempted to flying without the FMS to complete the flight, but open descent did not work.  

This is  a known issue, don't know when they are going to fix it....really annoying !

OK - thanks for letting me know.  Is there a known issues list or database or whatever so I don't have to keep posting stuff they already know about?