I went onto railjack to do some casual credit farming and found that my gunner crewmates wouldn't gun.
I'm on the most recent PC build, I went directly into a solo railjack mission from the relay's navigation after trading with Baro, and neither of my gunners would actually fire their guns. This persisted after I went back to Dry Dock and returned to a mission. However, a fresh login seemed to fix it, even after retracing my steps.
I did manage to record a video to show the bug happening.