Bug: Spy: The Diamond Back has the ability to award crit shots for each backstab or building sapped by the Spy. However, a bug exists where even if backstabbing someone who is invulnerable, like ubercharged or under the influence of Atomic Bonk, will still award a crit shot despite not killing the person stabbed.
Revealing mistake: Spy: Except for the default Revolver and Enforcer, the Spy doesn't actually put any bullets in his gun when reloading any of his pistols.
Bug: Any strange primary weapon for the Pyro can have the Strange Part: Underwater Kills added to it. However, the primary weapons for Pyro do not work under water, and any player ignited by the flamethrowers are instantly extinguished the moment they land in water, making it impossible to get any underwater kills with these weapons.
Bug: Scout/Engineer: The misc for the scout called Ball-Kicking Boots spawns a team colored soccer ball with the player that can be kicked around the field similarly to the TF2 birthday beach ball. This can not be destroyed by most things. However, the Short Circuit weapon for Engineer can destroy this as if it were a projectile.
Bug: So far, I have only found this glitch in Dust Bowl on the second capture point in stage 2. On the Red Team side, exiting the starting room, you see a folding down garage door that is always shut. Sometimes, it will be off set. The door is not connected right, and actually sticks out into to the walk way. Players can walk through it, and can't go in the door though due to an invisible wall.
Bug: Mann Vs. Machine: I have found that sometimes, when the wave is failed and the Machines successfully drop the bomb into Mann Co. a glitch happens that I have discovered with The Heavy. After a wave has failed, the Mann Co. Defenders team does the loser position where you can run around with hands in the air. But sometimes the Heavy will be completely invisible to the person playing him. Not sure what causes this, and so far only discovered with The Heavy.
Character mistake: Spy: The Spy is French in origin in this game, being a secret agent from some French agency supposedly. And thus voice actor playing him, Dennis Bateman speaks his lines with a French accent. However, when the Spy says lines in the game in his native French language, Dennis' English accent is heard through the French dialog.
Bug: Players are able to customize a tag which they can spray on most locations on the map. After a tag is sprayed, any player who looks at it gets a red text display saying SPRAYED BY and then says the person's name. If the player that sprayed the tag, then leaves the match, their tag will disappear. However, if any player looks at the spot where the tag was, they still get the text pop up saying there's a tag there and who it's sprayed by, only there's no tag.
Continuity mistake: When wearing certain cosmetics, like shirts for Spy, sometimes when switching to a different team the color of the cosmetic won't change on the body of your character. Like having a Dead of Night on spy, and then switching from BLUE team to RED team. His body hits the floor changing his outfit to red, but his shirt will remain blue.
Audio problem: Spy: The Spy has a voice response trigger sometimes when getting hit by the Sniper's Jarate (jar of piss), where when he sees it's all over his nice suit he yells "Jarate!? Nooooooooo." This same voice response will sometimes be triggered if they spy is hit with the Scout's Mad Milk, even though it's not Jarate.
