If you can mind control someone on the opposing team, and have the mind control active when they die, they will not be able to ressurect. They are now tagged as your faction and can't find a graveyard. It's possible that the only way to fix this right now is to log out/log in or afk out and get the deserter debuff.

Steps:

1. One faction priest (or possibly an engineer with MC cap) casts MC on opposing faction team member.

2. MC is still active when they die.

3. The dead player is now out of the game for a while.