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)
Revealing mistake: When Nova blasts through the building, the wall where the hole is created has already been drawn as misshapen and discolored, likely to make it easier for the animators to animate. (00:02:53)
Silence My Companion, My Death Destination - S1-E4
Revealing mistake: When Van Cliburn is playing the piano, some of the keys he strikes do not depress. (00:06:08)