I am on our second set of Wahl clippers, current pair being the color version or the next higher cost ones up (without a ton of accessories). I had thought it was just cheap clippers, at first, but after the third cut, they seem to start pulling at my son's hair -- and the last haircut was, well, not good. (hair on top did not cut as short as on the side, despite using the same blade guard, running over it a few times, etc).
I oil every 2nd use, too. It seems that about half way through they just stop cutting as well. I think it is his extremely thick and coarse hair. Am I the only one to have trouble?
Anyway, this photo is the sort of challenge I am faced with before cutting with the clippers. (not my son, internet photo)