Revealing mistake: When he's attacked in Down Below, Dr. Franklin is shoved against a station bulkhead/wall that wobbles when he hits it. (00:15:30)
Sins of the Fathers Chapter 1: Doctor Strange - S3-E1
Revealing mistake: When Mary Jane and the other servants of Baron Mordo are flying through the city, they literally disappear into thin air. Probably a problem with rendering the 2D animation within the 3D animation. (00:01:00)
Behold, a Distant Star - S2-E10
Revealing mistake: When the heroes are in the Fantasticar looking for the Skrulls, they fly by the same group of three buildings seven times, and from two opposing camera angles. (00:15:02)
Revealing mistake: When Dark Aegis is saying "But, I'll help you take that step by doing the next one with you," the edge of animation cel is visible on the left side of the screen. (00:15:37)