Continuity mistake: When Garrett is jumping on the bobbing things we look down on him from above. He has one more thing to jump on before he reaches the other side. Then we see him from a different perspective and he has to jump 5 more.
Continuity mistake: In the beginning, Sir Lionel leaves for Camelot in what looks like spring or summer. Camelot is 3 days ride, and Sir Lionel gets killed on the day he arrived. Three days travel back (totalling 6-7 days) and it shows the dead of winter.
Continuity mistake: Near the end, when Garrett leaves Kayley on her own with Excalibur, she is looking forward with no one around and when she turns back, Ruber and his gang immediately appear out of nowhere surrounding her.