When did the Bug occur?
It occurs during Chapter 15 after "Rosetta" has been reassembled and Issac begins the activation sequence to create the codex. If Issac is wearing two specific suits there are slight animation errors. If he is wearing the Engineering suit from Dead Space 2 (part of the "Dead Space Legends" set you get after beating the game once) as his helmet is disassembled and put back into his suit there is some sort of black lines that frame his head just for a second or two. While brief it is a very noticeable animation glitch during the cutscene. See 0:02 to 0:05 seconds in this video to see what I mean. Another slight but not so bad animation glitch also happens with the Archaeologist suit you get during the game. You can see the arresting hook that grabs the back piece of Issac's helmet protrudes from his back for a bit. As far as I could see all the other suits did not feature these modelling errors and were fine.
What did you do before you experienced the Bug (please be as detailed as possible)?
These glitches occur using the Engineering suit and the Archaeologist suit respectively during this cutscene. The worst culprit is the black lines surrounding Issac's head with the Engineering suit. I noticed the error with the Archaeologist suit only when looking for similar modelling errors.
What did you expect to happen?
It is more a question of what I did not expect to happen and what I did not expect to happen was such a weird animation glitch during a cutscene that, no matter how brief, is pretty noticeable. If possible I would like to see this addressed in a future patch for this game so all animations in all cutscenes perform smoothly.