Not being fully dilated can certainly be a sign of hypocalcaemia and a dose of calciject will definitely cause no harm, and can fix it if required. Technically it's not a true ringwomb as this means the cervix cannot be dilated with manual pressure, but a relative ringwomb as the muscles haven't relaxed properly. It can be due to dead lambs, lambs not positioning properly to stimulate the cervix to open, and a frequently forgotten problem is low calcium.