I'm getting a new message here:
Turrets don't really do much, sitting in one spot until they identify a target and fire. You pull out the most interesting bit you can find, though.
All these clips of drones fighting have started to blur together.
The above is appearing for all four drone memory chips (now that I've used too many) when you would normally gain XP. I'd suspect that the number of memories you can successfully use is somehow capped by your stats (Perception?). Buffing Perception didn't seem to help, not that I really expected it to.
I've used 80 (non-autoturret) memories today and no drone signature. I also suspect that the requirement for learning that is not 60 memories total — but more like gaining 20 XP. I'll try some more tomorrow.