Dark Phoenix (1): Dazzled - S3-E11
Continuity mistake: When the X-Men first enter the Hellfire Club, Gambit's black pants are incorrectly colored blue. (00:19:03)
Dark Phoenix (1): Dazzled - S3-E11
Continuity mistake: When Gambit throws a kinetically charged playing card at the White Queen, Wolverine is directly behind him, and Beast is behind him and to his right. A couple of shots later when Pierce has lifted Gambit by his collar, Wolverine has disappeared and Beast approaches Gambit from his left. Wolverine then reappears in his original spot after Pierce throws Gambit at Beast. (00:19:09)
Dark Phoenix (1): Dazzled - S3-E11
Continuity mistake: When Wolverine slashes at Donald Pierce's arm, the sleeve of Pierce's jacket is torn around the elbow. When the shot changes, nearly the entire sleeve is torn off. (00:19:27)

The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Sebastian Shaw is warning the White Queen not to fail the group, the pitchfork-like pin on his jacket disappears between shots. (00:04:10)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Wolverine is giving the Dirty Harry speech to the guard, the distance between the two of them varies depending on the shot. (00:05:24)

The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Beast says "We appear to be at the mercy of our hosts," he is noticeably further away from Cyclops than he is from the rest of the episode. The captive X-Men are chained to the floor with not much slack, so he could not have simply moved away from Cyclops on his own. (00:05:50)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Sebastian Shaw is escorting Jean out of the room, there is a chair with a side table in the foreground. A couple of shots later when Wyngarde is sitting in the chair, the side table has disappeared. (00:06:09)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When the White Queen is telling Shaw and Wyngarde to think, there is a painting on the wall to Shaw's left. When the shot changes, the painting has disappeared. (00:06:28)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Wolverine emerges from the dumb waiter and kicks the waiter against the wall, the waiter ends up beneath a painting. When Wolverine walks toward the turkey, you can see the painting on the wall, but the waiter has disappeared from beneath it. (00:07:24)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Cyclops is trying to reestablish his psychic rapport with Jean, his head gear stops at around his eye level when it normally goes up to his hairline. (00:08:20)

The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: The "X" mark torn into Cyclops' shirt changes size and position a few times. (00:09:50 - 00:11:10)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Cyclops collapses to the floor, his normally yellow visor is now colored blue, and Gambit's normally black pants are now colored light-blue. (00:11:35)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When the White Queen is probing Cyclops' mind, the neck part of his head gear is flesh-colored. (00:12:10)
The Dark Phoenix (2): The Inner Circle - S3-E12
Audio problem: When Wyngarde says "For new sensations, my love," his mouth is closed for most of the line. (00:12:50)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Sebastian Shaw begins questioning the loyalty of the other Inner Circle members to him, Wolverine is collapsed on the floor next to Shaw and Leland. Moments later when Shaw walks over to the White Queen, Wolverine has disappeared from that spot. (00:13:44)
The Dark Phoenix (2): The Inner Circle - S3-E12
Revealing mistake: When Cyclops uses his optic beam to blast Leland through several walls, the final wall that Leland goes through already has a hole in it. (00:15:40)

The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Cyclops blasts a hole in the floor beneath Sebastian Shaw and causes him to fall through it, Shaw lands on a catering table. Later when Beast jumps down the hole to attack Shaw, Shaw is emerging from underneath heavy rubble rather than a catering table, and he is inexplicably shirtless. The rubble also changes from being brown just before Beast jumps down the hole, and is then white after he lands. Additionally, the floor goes from being black-and-white checkered to a solid brown color. (00:15:55 - 00:17:05)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: The hole in the floor that Sebastian Shaw falls through is suddenly larger when shown from the underside. (00:16:00)
The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: The pink patches are missing from Gambit's pants when the White Queen blasts him against the bookcase. (00:16:05)

The Dark Phoenix (2): The Inner Circle - S3-E12
Continuity mistake: When Cyclops and Beast are cornering Wyngarde, Beast's entire belt is red, when normally his belt is yellow and the X in the middle has red around it. (00:16:20)
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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