While not a bug per se, nor ruining gameplay experience in any significant way, this issue proves to be rather uncomfortable.
In a Corpus Outpost tileset, a dropship may spawn to carry a platoon of crewmen. This, while an interesting sight and interaction, may unnecessarily prolong the gameplay with no alternative but to wait for it to despawn: since the dropship is invulnerable and counts as an enemy, the every fifth wave (after which a rotation and an extraction window appear) doesn't end up until it teleports away, thus demanding the players to wait for an uncomfortable period of time.
Possible solutions:
1) hard-code the dropship not to spawn during multiple-of-five waves
2) make the dropship vulnerable to damage (possibly, vulnerable only to archguns like Profit-Taker's health)
3) make the dropship not count as an enemy unit as of itself.
Case in point, a screenshot of an invulnerable dropship:
Thank you for your consideration.