Referencing the scene where Optimus is flying into the crowd of decepticons. -Optimus lands, see a red car start flipping sidewides followed by a black car in tow -switch scene -Optimus throws gear away and swings out his sword, you see the red car clear as day followed by the black car. Dammit the red car gave it away the effect again. Curse you red cars!
I think this might be the thread you want to post this error. http://www.tfw2005.com/boards/transformers-movie-discussion/423703-errors-jokes-references-hard-spot-things-dotm.html