There is a mission, where I have to repair the dashboard of a small boat. This boat was close to land. When getting into the "mission zone" the framerate suddenly went to 2fps, making the game unplayable but I was able to get to the boat and do the repairs. After the repairs were made (mission success), the fps went back to normal. The hole process from entering the mission zone to the completion of the mission took me 1h and 12min, but I hope this helps to eliminate the error.

As long as the game has gamestopping bugs, you have to give the player the possibility to somehow continue their game, in this case: Give us the possibility to get rid of a mission (right click on the mission icon and select "delete mission").

And of course: Don't disable the noClip-function in career mode, because this function can also help to prevent frustration.