I was recommended to bring this problem to these forums… I’m still not sure if I’m in the right spot. I’m just going to copy/paste what I had on the other Microsoft forum, but for reference the post is here: Microsoft Forum Link
I was directed here by Xbox Support Chat… This isn’t a huge deal, just a programming/database bug.
On the halo waypoint site under ‘Challenges’ on the left, then ‘Campaign’, and under ‘Spartan Ops Weekly’ and under ‘Episode of Legend’ it is reading “Complete all missions in Chapter Id -1 is invalid. on Legendary difficulty.”
The page in question can be found by going to https://app.halowaypoint.com/en-us/#Halo4/stingray2772/challenges
… somebody mentioned in my other post that it was in the game that way too, but I think I checked that and I couldn’t find it.