Both Rabbi Heineman and Rabbi Forcheimer hold each Norelco has to be checked by am expert in the field. Until they are checked, they are prohibited. And they seem to be basing this on Reb Moshe zt”l.
Rabbi Heineman says one blades are prohibited, and Rabbi Forcheimer said it is a “taar mamash’.
Rabbi Blumenkrantz is no longer alive to ask, and the children who put out the sefer never spoke to Reb Moshe ztl.