Strange phantom UESC Cargo Drones in Perimeter

On Perimeter, near South Relay in Columns and by Station, you can hear the audio of a UESC Cargo Drone flying overhead, but no bot is present, as well as no gibs of a drone and it's cargo box. Attached are three video examples of it, from two separate runs. I will note that these were taken on Sponsored Survival Perimeter so it may potentially be related to that.
https://outplayed.tv/marathon/bGKDGz 
https://outplayed.tv/marathon/KzZVze
https://outplayed.tv/marathon/Ddm6dy