I believe to have found a bug with the kennel engineering station.
I don't know where to report it, so, for now, I'll describe it here, if I need to report it somewhere else please let me know.
If you build a t2 kennel and upgrade it before the construction is finished no drone is built along with it, and once the upgrade has finished a new t3 kennel appears on top of the original one with it still existing.
everytime the original kennel is upgraded to t3 a new kennel is created on top of the original one with 2 new drones.
I recreated the bug as best as I could in a sandbox game. the replay ID is 8730971.