I did a T1 bounty in the Vallis and the "Defend the Drone" stage popped up. This is where a drone has to be shot down and then defended against enemies. After 30 killed enemies the stage is complete. I killed everything there was and what spawned in, including the Coil Drives, for a total of 27 kills. Then spawn rates slowed down significantly, making me believe the stage was broken at first. After some minutes, one enemy spawned in and another ~4-5 minutes later a batch of 2 enemies spawned. In total, the stage probably took about 10 minutes.