Hi Peter,
That is strange as the larger stars are not duplicated, but some of the smaller ones are in lines I make to be 19 long, with some gaps, so maybe close enough to 24 as some may be one on top of the other.
I would have a careful look through of all your 24 subexposures, flicking back from one to the other to see if you indeed have some sort of star movement, but given the larger stars and the central nebula don't appear smeared I don't think you'll find any. That then suggests some form of error in the stacking routine. Perhaps try to repeat the stacking with different stacking software and for the heck of it redo the stacking with the original software you used in case there was some form of transient glitch or incorrect setting.
Best of luck
Best
JA