Some bugs I've found:
- Souls dropped from the Soul Collector perk don't appear if the enemy is on a higher plane than the main plane. Such as when playing the Skyscraper map, souls on the ground level appear properly, but once you ascend, there aren't any. Possibly they appear at a fixed Z-position on the base plane.
- I beat the main campaign, and without quitting, tried out the Endless and Single stage modes. The HUD did not appear in either mode. Quitting and restarting fixed it. My guess is that when the HUD is disabled for the end sequence, it might not be re-enabled if you start a new game or game mode.
- The minigun turret will target the exit gate, but won't stop firing even after its dead.