(Original Post)
are you setting it to transmit SPI to wingmen with DMS Long Left (del key), then targeting the Air defense with your TGP, setting it as SPI and giving your wingman the order to attack with missile the air defense ? or are you sending the wingman in blindly?
Also use F2 to look at your wingman and check for any damage, I find if he is hit by sam or shot up too much he will jettison his ammunition. When he has no ammunition to attack with he will either just rejoin or say "unable".
I know this video is "old" but I find if I use commands to the wingmen in this manner they behave according to what the video shows;
(EDIT)
Bug Found and Reported
The problem is not in any "specific mission", It affects all missions. The Artificial Intelligence of the wingman has a problem switching from Gun attack to any other form of attack.
To re-produce the fault
Load up Any instant action mission, task the wingman to destroy a target with Gun, allow the wingman time to destroy the target and rejoin.
Then task the wingman to destroy a target with missile or bomb, the wingman will no longer be able to attack (fault condition achieved).
( Once I had a rare occasion where the wingman was still able to attack with a bomb at the next waypoint, I allowed him 1 pass with the bomb and then tasked him to complete the attack with Gun. After that the fault occurred. )
Temporary Workaround
Avoid telling the wingman to use the gun. All other directed attacks ( ie with missile, bombs, etc) should be ok, but once he is in gun mode, thats all he will use.
Fault Status
Nate (ED Testers Team) has taken a look at it for us.
He has Reproduced the fault in a simple track and reported it.
Hopefully a fix is on the way.