I bet you had moved into the gunners position earlier.
There seems to be a problem if you jump into the gunner's position and get out again, the gunner does not return to automatic mode.
I have not confirmed it myself but I never switch into the gunner's position and I have the privilidge of my gunner informing me about any enemy planes approaching (on a ME110) and keeps tracking them with his head and gun.
~S~
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