In one of my videos, I talk about and make references to a trailer that plays throughout. It's cropped to less than a quarter of the screen and all of the audio is created by me - absolutely none from the original trailer. Within 2 hours of posting it was flagged for 3rd party.
They generally don't flag trailers for copyright since any publicity is good publicity, but they will certainly flag it for 3rd party and any ad revenue from it will go to them, not you.