When you create an auto-cannon above your head there are several different bugs I've encountered!
1st possible bug: The cannon falls on your head and stops there. No bug you think? Well, it is still there hanging around in the air if you go away.
2nd possible bug: The cannon bounces off your head and takes the place next to you - but above and/or around the cannon are additional tripods (without a cannon).
3rd possible bug: The cannon bounces, but suddenly there are two cannons at once (next to each other). It gets even stranger as one cannon is first of all working correctly (firing enemies) while the other cannon seems to attack its twin. The correct working one disappears after some time and the other one then becomes normal...
Also I've got a problem with spawning weapons with the scientist. When switching to this inventor gun I can spawn the Tomahawk gun (although I'm not able to carry it - my teammates are). Great idea, but when pressing the alt-fire once it switches to the phasors to spawn. I'm not able to switch away from the phasors any more. Even weapon-switching doesn't help. If I press alt-fire it only displays that I've selected to spawn phasors again.