Exterminate Kill Count

[(XBOX)Tzelathias]

I have not seen any one with this particular bug from the Archwing Balor Fomorian mission.  According to video there should be a kill counter for the mission in the lower left corner.  On spawning in the mission, I have no kill counter.  I have tried killing as many as 150 enemy to see if the raw number would work despite the lack of a counter. (I noticed on one video the count went up to 117)

After killing 50 or 150 or any number, I get the point for the Archwing drop without problem.  I can even make it to through the debris field very rarely even getting hit by the big gun.  Regardless, at some point I pass a threshold and I receive the following message, " Mission Failure eminent.  Eliminate all remaining enemy." with a count down timer from a minute which to date always expires.  In my mind the problem is the counter and the count never being registered. (I could be wrong in this assumption)  Has anyone else had this problem and was there a solution.