Just found a weird glitch.
When you're using Trevor during the side mission with Cletus, you'll eventually drive to the abandoned motel and shoot the tires of moving cars. If you immediately start shooting tires with your rifle before Cletus mentions anything it should start the glitch shortly afterward. Cletus will tell you to start shooting the tires, and then immediately say "Nice shooting Trev" or something like that, and then he'll want to proceed. If you stay behind and shoot 3 more car tires he'll continue moving forward to the next spot. Chase after him after you've shot the tires. You'll then go to shoot coyotes, you'll get to the roof and he'll immediately say "Nice shooting trev" without you shooting any coyotes. He then proceeds to walk away (as if the mission had ended) yet he remains a blue dot on your GPS as if you're in the middle of a mission still. I ran into all of this on the mission. I couldn't move past it and get a mission pass. I attempted going to my safe house and saving the game, it wouldn't let me. I even got into a vehicle and ran Cletus over several times trying to fail the mission, it wouldn't work. I had to run into a nearby swimming area and drown myself to fail the mission and restart it all over again.