Revealing mistake: When morphing, a "Net" appears over the Rangers, which their Zeo powers then morph them over. Tommy and Tanya's nets don't match their bodies - for example, their shoulders aren't in the net, yet they disappear when their Ranger costume appears.
Helping Hands, Iron Fist - S1-E4
Revealing mistake: When Iron Man appears on the screen in the Hulkbuster armor, if you look at the background behind him, there is a closed door behind him to his right and a control panel directly behind him, which means he appeared from out of nowhere.