I used the golden tickets to get rid of 15 assignments that I either couldn’t or didn’t want to do, but I still had 12 available (not yet complete) on the list you can see in the background, behind the golden ticket prompt. None of those have been started.
For some more background: the golden ticket feature allows you to replace one of the available assignments on the screen with a substitute. You can then choose any one of the displayed assignments to complete.
It does not make sense to me why I now can’t complete any of the remaining 12 after I passed on the others simply because there are no hidden, alternate assignments left. I think the screen being locked is a bug.