I failed a test and my instructor believed it wasn’t justified, and said that it should be appealed, however, if they do allow a retest, you have to have two examiners with you. Obviously that means it’s going to be a lot harder and it’s probably not worth it.
I don’t think the indicator thing should have been a major, but it is your own responsibility to make sure you turn it off regardless of whether the car normally does it itself or not. It is a mistake though, someone could have thought you were turning and pulled out on you, or cars behind could have thought you were pulling over and overtaken etc
Good luck on the next test!