Not sure if that's the reason Scott doesn't produce the Session anymore, and I don't know if I'd call it a big argument...but it was sometime early 2016. Im currently on June 2016, and its been Beevo for the past few "months" of shows. I don't remember the exact show date.
I'd say it was more friction between him and Justin. Moscow brought stuff in like the soundboard that Justin didn't like and there just seemed to be friction between the two over how to run the show. Him running the sour hour is the best solution, as Justin doesn't have to actually work with him then and Moscow only really has to answer to Jay Goodwin, who seems to like the silly-lame style he brings.
Uff yeah, what happened to the large number of people who used to go on the show? Is Concord a long way away from where they live compared to Justin's house? They could try to get some of the people from the other shows onto the Session to try to inject something different. Porno Steve seems like he'd be a lot of fun on the show, maybe they could get him onto it.
They also seem to not give a shit about the fact that new shows are starting on the BN, not giving them a shout out. I learned about Bikes + Beers because Moscow mentioned it on The Sour Hour, and I found out about Shinerunner because I was randomly browsing the site.