A controversial Andy Williams strike ended Swindon's unbeaten league start as the Robins lost 1-0 at home to Northampton to drop off the top of League Two.
Former Swindon striker Williams crashed a half-volley in off the inside of the near post after 67 minutes, but appeared to be offside as the ball reached his feet.
It led to lengthy complaints from Swindon players, management staff and fans, however the minds of the officials were not changed.
Swindon would have been level in the 73rd minute had Adam May kept his shot from about 12 yards down as it instead flew over the bar, as Northampton clung onto their lead.
Lloyd Isgrove and Jordan Turnbull shot over and wide respectively for each side in the first half while Jordan Lyden had a header well tipped over the bar by Northampton's David Cornell in the second.
Tyler Reid and Michael Doughty also came close to levelling for the hosts. Reid had an effort deflected wide and Doughty's last-gasp free-kick went over.