Night of the Sentinels: Part 2 - S1-E2
Other mistake: When the Sentinel throws Wolverine over the trees, you can hear him crash to the ground as soon as his body disappears from view. The ground in the area is flat with no tall hills, so Wolverine would require another second or two after clearing the treeline to crash to the ground. (00:10:24)
Night of the Sentinels: Part 2 - S1-E2
Other mistake: After Storm and Cyclops fly away from the barrage of Sentinels, one Sentinel is shown to have his right foot "floating" on top of the left foot of another Sentinel, almost as if their feet were occupying the same space. (00:11:25)
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.
BaconIsMyBFF