I went to do the daily event "Hotshot: Bolinas Sniper is a Hotshot challenge" that is located in Marin, near the far West end of the map. I failed it the first time trying it, so hit "A" button to redo it. Well the first time I did that, the timer started at 1 and none of the NPCs loaded on to the map, I waited for a bit and nothing happens, so I jumped off the platform to restart it and this time it loaded the mission to stop the plant from blowing up, the NPCs started to show up and glitch about. They would appear then disappear then Reappear, and I was still up at the sniper platform. So I jumped off again to restart it again, and again the timer started at 1 and no NPCs. so I jumped off again but this time I left the challenge.

That seems to have worked to reset it, as I went back in and it started to work ok, but then I failed again and hit the button to restart it again and the bug started again. it seems that you have to leave the challenge then go back to get it to reset itself. I hope this helps anyone else that is having a hard time with that challenge