Grand Theft Auto V gépigény

Mission unable to start
"The mission has been disrupted. Try again later."
This happens everytime i try to start an FIB mission which is avaliable straight after the train heist. It seems to occur whenever one of the other playable charcters is near to the start location... they appear to be waiting there, everytime i drive dpwn to the mission start.
I have tried to start this mission with every character with absolutely no change. Has anyone else every had this glitch and is there a way to solve it without starting the whole game again?

Ok, here is how I did it: Ran up the mountain, waited for the "B" to return on the mini-map, indicating the mission was playable again, then walked down the mountain but continuously looking through the sniper scope. Walked all the way to the pier and then put down the gun (stopped looking through the scope). Cutscene starts. Did it as Michael in case that makes a difference.