Halo: Reach Backwards Compatibility Issue?

I started playing Reach on my Xbox One, again, because the bugs were finally fixed. My question has to do with Firefight. I used to play Firefight for hours to build up credits, and I’d earn them in the thousands. Now, though, on my Xbox one, I’m only getting 50 credits no matter how long I play. It’s also not loading up my customized matches, but I’m more annoyed by the credits thing. Is there a fix for this I can do, or is it yet another bug in the Backwards Compatibility?