Apologies for the late reply! This is a known issue introduced by the latest update, which made some changes to tooltips for burst-fire weapons. One of those changes causes an issue with the Vanguard Missile Pod, making it impossible to craft the weapon. I'll try and push out a quick hotfix for it soon: I was initially hoping to release some new content along with that hotfix, but development of that new content is taking longer than expected...

This happend to me once when i tried to craft it in Admin mode