Clermont Auvergne, last season's Heineken Cup semi-finalists, went back to the top of Pool Five thanks to a 13-minute burst at the start of the second half on their way to a 46-12 win at Exeter.
The visitors were quick off the mark at the restart, scoring 15 points to regain the lead - which they held on to and increased without reply.
Exeter will question the services of the TMO as their England flanker Tom Johnson appeared to have tackled Clermont Auvergne's centre Wesley Fofana - who went on to score a try in the corner early in the second half which changed the face of the game.
Julien Bonnaire also crossed in that spell with Morgan Parra converting Fofana's try and adding a penalty.
Napolioni Nalaga added two tries, while Sitiveni Sivivatu and Fofana also crossed.
Fly-half Gareth Steenson kicked all of Exeter's points from four first-half penalties.