The Doc must be 120 yrs old to know all this stuff! Ten radiators, how many zones? Are all zones balanced for equal pressure drop? Water, like voltage,takes the path of least resistance, and will flow through "easiest" zone or group of rads'. As Doc says, bleed em again. Contact the rad maker and ask if it's possible to fit air separators at the top of the radiators in the zones giving trouble. Air separators at the highest points of your system might be a good idea anyway. There ought to be an expansion tank-air separator setup directly after your furnace & pump, if not, that's a good idea too. Happy Heating & Happy New Year, The Waterguysers.