As they cross the river and into the field on horseback, there are only 5 horses crossing the clearing but there should be 6.
At one point in the Abandoned City, the darkness spreads and dissolves one of the horses. The other horses flee in terror. Moments later, once the four young protagonists are separated by the spreading darkness, you can see the white horse still tied up as two of the protagonists run away.
After being questioned by the Children of the Light with no ring on, Moiraine is riding next to Egwene and you see the blue ring on, but it's not giving back to Moiraine by Lan until the next scene.
As they are approaching Shadar Logoth, the horses all stop and Egwene can't get her horse to move. After Lan says, "Come on.", the horses are all calm and proceed without incident.