Engineer Specialist 3 and vehicle repairs not working

I'm currently trying to do the Engineer Specialist 3 challenge, but for some reason the challenge does not progress. I've spent the last 5 matches only running around repairing friendly vehicles and it hasn't progressed a single point (I know it has to be done in a single match, but when I was checking mid-game on the progress for this challenge it didn't progress). I also have noticed that sometimes I'm not getting score / XP for repairing vehicles. Please fix.