I have a similar question. Since the neutrino's has a rest mass I can observe it in a SR frame where it is at rest. Now if I measure the mass (say by energy absorption inside a light trap) at one time. To the degree necessary to distinguish it's state from the other neutrino states I get a number and corresponding energy. Now if I measure it later when it has morphed into another flavor; where is the extra/deficit energy? Or is it, that once I determine the mass the flavor is fixed forever? My knowledge of QM is such that the link "this thread" is difficult. Is there a possibility of a simple answer to my experiment? I do realize this sort of thing apparently happens elsewhere in QM but I don't understand that either and there seem to counterbalancing energy carriers in the cases I know about.