Night of the Sentinels: Part 1 - S1-E1
Plot hole: Wolverine bails out on the mission to destroy the files at the Mutant Registration Center to instead go look for Jubilee after she goes missing. When the rest of the team arrives, Wolverine is already there waiting for them. They flew to the Mutant Registration Center in a jet and their mission briefing heavily implied that they needed to leave immediately, so there is no way Wolverine could have arrived before them if he was off looking for Jubilee first.
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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