If you quit client mission 4 before repairing beacon you lose your access to field agents deeming you unable to continue with missions unless you start over from the start. Not sure if this it occurs after this specific mission also, not feeling like starting over right now so can't test it.
I believe you can start over from Mission 3, rather than from the beginning, as a temporary workaround while the devs work on the next alpha release
Nope, it's not possible since NT4 remembers my currently active mission and there is no abort button ( and you can't start mission while you're on another active one) So if you get stuck like this it's either all or nothing
So the command "stinger-reset 3" doesn't work for you? That should reset it so that you begin on mission 3.