I picked up the New Light questline early this season so I could experience the new intro and get easy leveling gear. However, after running through it and getting the crucible/vanguard/gambit questlines, I noticed that the gambit one seemed to be stuck. Step 4/5 of the quest (that requires you to get 4,500 infamy) seemed to be increasing a LOT slower than my actual infamy rank. My friends told me I was crazy and so I didn't really pay close attention to it, figuring I'd finish it eventually. After about 3 weeks I hit 15,000 infamy and reset my rank, and when I checked the Quid Pro Quo quest later that day I noticed it was back to 0/4,500 infamy. I was kind of annoyed, but again decided it would get done eventually.
Today I was going through my quests to make space for bounties, and I checked on the Quid Pro Quo quest. I'd done a few games of gambit since the infamy reset, and the in-game quest progress hadn't gone up. At all. And looking on the mobile app shows that my quest progress is at -996714/4500. I haven't abandoned and reacquired the quest yet to see if it fixes the issue, but an issue like this shouldn't be there in the first place, especially for New Light players.