If you could provide us more details of line and such of the error message, that would be very beneficial. Where you were in the routes, what specifically you did, etc. Screenshots would also be good.
Apologies, but I didn't run into the error a second time when I skipped through the dialogue to see if it would pop up. I am 90% sure the error occured after mason said he would keep to the 'date' plans with Elliot. It might be best for now if anyone experiences the same thing in the future to advise them to not start freaking out until quitting and reloading their game.