Revealing mistake: The film was rushed to theaters, leaving a few mistakes which Universal fixed. In the original cut, toward the end, Judi Dench's human hand is visible, complete with her wedding ring. This was fixed for the re-release.
Continuity mistake: When Victoria is released from her bag, it lies around both of her feet. When the shot changes it lies next to her right foot.
Continuity mistake: Gus closes the curtains with both hands but from the opposite shot he is only using his left hand.
Continuity mistake: When Bustopher is on the plank and another cat is on the opposite side holding a towel (or something similar) the length of the part behind changes from short to long with no continuity between shots.
Continuity mistake: Bustopher falls backwards on the lid and slides down facing a 6 o'clock position. When the shot changes he is in an 8 o'clock position.
Continuity mistake: When Bustopher comes out of the trash can and sings "I'm frequently seen" Mr. Mistoffelees slides down the can from the top to the bottom. When the shot changes he is on the upper part again.
Continuity mistake: Jennyanydots says Bustopher wants to reborn to eat again. He points at her with his right hand and then bends his arm. When the shot changes his arm is extended again and he is repeating the previous movements.
Continuity mistake: When Jennyanydots sees Bustopher she slaps his tummy and raises her left arm. When the shot changes it's lowered.
Continuity mistake: When introducing Jennyanydots, Munkustrap says "and that's what makes..." and Jennyanydots smacks a can. The cat on top has one leg on top of the other or not, depending on the shot.
Continuity mistake: When Jennyanydots is scratching her thighs a strand of wool is stuck to her foot or not, depending on the shot.
Continuity mistake: When we're introduced to Jennyanydots there's a strand of wool falling right through the middle of the yarn. A shot later it is behind the yarn.
Continuity mistake: Outside on the railroad tracks, when Skimbleshanks sings "When Skimble was about and on the move" Victoria's position changes in every single shot: First she is sitting sideways with her legs on the left side of the tracks, then she is looking straight at him and, finally, her legs are suddenly on the right side.
Continuity mistake: When Skimbleshanks sings "Of the Sleeping Car Express" the number of cats around has no continuity: Sometimes there's none, others one that suddenly swap to three.
Continuity mistake: Skimbleshanks sings "for the Northern" and the cats approach the railroad tracks. In the immediate shot, when he sings "hemisphere" the cats are away and approach again.
Continuity mistake: When Victoria lays in bed with the two cats the pink cushion on the left has feathers all over. In the immediate following shot there are feathers only on the upper part of the cushion. Then it swaps back to the previous shot.
Continuity mistake: When Bustopher sings "I am still in my prime" all the trash and mess on the floor magically disappears and everything is neatly piled on a circle for him to stand on.
Continuity mistake: Bustopher is crouched singing by to the opening of the trash can, but after he says "I put on weight every day" shot changes and he is standing up behind the can.
Continuity mistake: In the train when Skimbleshacks sings "and was ready to remind him" a cat on the left of the sink suddenly appears on the middle part.
Revealing mistake: The first front shot of Skimbleshanks outside on the railroad tracks with the cats behind, the cats don't cast a shadow and seem like they're floating.
Continuity mistake: When in the train the cats sing "bothered by mice" the cat in the sink changes positions between shots.
Answer: The issue wasn't about her hand looking human but, as you mentioned, that she was wearing her own ring, which was digitally removed in the revised version.