Secrets, Not Long Buried - S4-E15
Continuity mistake: During the battle at the end, Cyclops uses the crystal statue he brought with him in the fight by throwing it into the air and uses it to refocus his optic blasts on a crowd of attackers. After the battle is over he gives the statue to Dr. Prescott without ever having retrieved it. (00:18:55 - 00:20:20)
Secrets, Not Long Buried - S4-E15
Continuity mistake: The mutants that have gathered for Solarr's speech are in different places throughout depending on the shot. (00:16:50 - 00:18:50)