are the challenges working properly?

I've been trying a couple of challenges lately -
Rambo; it says you must complete the level without getting incapacitated by SI. I though incapacitated meant having so little life that you would be crawling. I completed the level but got caught momentarily by a charger but escaped immediately using my knife and lost hardly any life (was still way in the green). It said I lost the challenge.
Safe Fire; it says to complete the level without causing dammage to any other player. I tried this a twice and failed, and didn't think I hit anyone. Finally, I completed a level on this challenge without pressing any of the mouse keys (so there was no way I could hit anyone) - I failed. is it broken?

 

Only challenges that don't require the game to end work in any Co-Op server. Like Zombie Genocide.

On versus, most challenges do work.

On a side note you can activate challanges mid game somtimes but it can be risky if you went down or did friendly fire before you activate it.