Yes, it's that gig
restarted many times and not fixed
Going through the back ? Which also allows you to have the bonus easily.
What if you manually save before starting (before entering), closing the game entirely and relaunching it, does it persist ?
If yes, except report the bug
here, I don't know how you can solve that, it's weird.
(I never had this bug, and yet i have done this GIG a number of times)
Anyway, keep preciously a save before starting this GIG
(If you continue and leaving this GIG aside for now, do it from this save. Especially not when it's "blocked")