Ditto braise. Which, remember, requires enough liquid (beef stock) to just fully immerse the meat. It takes a little bit of attending, but I also do my lamb shanks stove top. And, I think I would leave the foil out. No pain no gain. Foil might also be acting as an insulator, working against heat conduction. It's worth your repeated efforts, steviegee, to get the shanks fall-off-the-bone tender. Good luck!