Warwickhunt is right: Stokes went off for a while after what looked like a collision of big men with arms up in the air. Didn't see whether it was deliberate. He went down immediately, then off the pitch, and yes, that's exactly when Exeter began their brief period of dominance against ten men in the first half. McDonald was getting stripped to come on in case.
The ref then had words with Stockley ('encouraged' by Doyle) before their man (possibly Stockley himself) bad-temperedly drilled the ball out of play from the 'drop-ball'.
Stokes came back on before a corner and immediately went to mark Stockley, whereupon there was much pulling and jousting. The ref reprimanded them both. Stokes played a couple of wayward balls (perhaps still woozy) then seemed to be fine again all game.
Could have been a key incident.