It seems there is a debug message reading "Selected Station X" and the player switches to "Bombs & GM ARM". This message is also displayed when the player launches 1 of 2 AIM-9P5s with both stations selected. I did not do a thorough test to see what every condition was, but at the very least you should replicate this issue with the following steps:
Open the "Caucasus A-4E-C Dogfight vs F-14A Veteran.miz" in Mission Editor
Add AIM-9P5s to the outer-most stations. Stations 1 and 5.
It seems there is a debug message reading "Selected Station X" and the player switches to "Bombs & GM ARM". This message is also displayed when the player launches 1 of 2 AIM-9P5s with both stations selected. I did not do a thorough test to see what every condition was, but at the very least you should replicate this issue with the following steps: