Thank-you for sharing your teacher's explanation of this puzzling
matter and for the Suddhodana quote from Sp V 1006 which I wasn't aware
of. I would like to pass on another possible solution, offered by Ole
Pind on my own list and supported by Lance Cousins, which is to
take "vandite" as an accusative plural in association with "paade" of
the previous sentence. "...tumhaaka.m paade vandaami, aya.m me vandanaa
ti. ra~n~naa pana vandite. . ." --- " . . . I honour your feet, 'this
is my third salutation'. And (his feet) being honoured by the
king, . . ." The same usage of 'vandite' with 'paade' also occurs at D
II 164. I hadn't considered this possibility before but it sounds
plausible to me.