Hello,
I can confirm that is probably a bug.
If I have equipped the NVGs, STING will not detach.
Without NVGs STING detach normally and attack the Migs at his target Point.
I have tried this multiple times and the behavior was every time the same.
I am on the OB.
By the way, it is a very good campaign. The difficulty slowly increases. A little bit to much A2A in my opinion. But I will replay it.
Greetings from Germany.
Hottie