This one from Ian Hodgetts in the UK isn't exactly a continuity error but I think it still deserves a place. Didn't they always say that it wasn't getting the hundreds of fans to clap in time that was the hard part, it was the four band members?!
"How about the part in "Radio GaGa" when Roger (I think) raises his arms too high so we can't see Freddie's face. I can almost hear the director scream, "LOWER, LOWER!!!" "