Night of the Sentinels: Part 1 - S1-E1
Audio problem: When Cyclops is saying "Okay Storm, do your thing," his mouth movement does not match the dialogue. (00:18:31)
Night of the Sentinels: Part 2 - S1-E2
Audio problem: When the tower guard is saying "Put me down, you flying freak," his mouth is not moving. (00:06:54)
Audio problem: When Professor X says "I was wrong Wolverine. I should have listened to you," his mouth is completely closed. (00:19:50)
Audio problem: When Callisto says to Cyclops "away from those who fear us," her mouth is completely closed. (00:09:20)
Slave Island - S1-E7
Audio problem: When Trask is saying "All it requires is an outside power source," his mouth does not move in sync with the last two words. (00:10:20)
Slave Island - S1-E7
Audio problem: When the decapitated Sentinel body crashes to the ground, the sound of it crashing against the concrete is too soft for its size. It sounds like something slamming against a metal appliance when it should sound more like a car crashing into a wall, only louder. (00:13:50)
Slave Island - S1-E7
Audio problem: When the giant wave of water from the burst dam is heading towards Cable, Hodge and the Leader, Cable begins laughing maniacally. After the wave crashes down on them and floods the area, you can still hear Cable laughing even though he should be submerged underwater. (00:19:25)
Audio problem: When Cyclops shoots an optic blast at War's feet during the battle at Stone Henge, the groan that War lets out is the same sound used whenever Wolverine's groans. (00:18:24)
Days of Future Past: Part 1 - S1-E11
Audio problem: When Bishop is saying "They treat the rest of us just fine," his mouth is not moving for the last two words. (00:04:53)
Days of Future Past: Part 1 - S1-E11
Audio problem: When Beast says to Gambit "Though I am always in haste, I am never in a hurry," his mouth is completely closed for most of the line. (00:11:30)
Answer: Chris Potter, the original Gambit voice actor, did indeed quit the role in the 4th season. His last episode was The Phalanx Covenant Part 1 so it seems reasonable that Fox would limit the use of the character even though it was recast. It doesn't appear that Potter left the role due to animosity, he stated in an interview that he wished to play Gambit in the first live action X-Men film.
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