I noticed a setting in the backend setup under Interaction between inputs, for "Schedule as group". I can't seem to figure what it's for or if I should be using it. Any advice out there?

If this is what I am thinking, it would sort of override the max recordings per tuner. Tomorrow I will find out if it is working. I have a couple dual tuner HDHomeruns with separate antennas for different channels and the max recording was set to 2 for each tuner. A couple weeks ago I saw a recording conflict because too many things were scheduled to record May 2. The first thing I was going to do was up the max recordings to 3 because there were 3 shows scheduled on the same multiplex. However, I looked at the details of the "schedule as group" setting and it appears that it will essentially allow unlimited max recordings per multiplex when enabled.

I'm sure it makes sense to the developers why they named it as such, but it seems obscure. Here's a link to some history from over a year ago when they were asking for testers for it. I stumbled upon it when I was asking the same question as you.
https://lists.gt.net/mythtv/dev/614305

Thanks. I saw that post about a call for testing the feature too. Just haven't found any good description of what it's supposed to do. I saw in the .30 fixes notes some "tweaks" were made to it. I'm trying to figure out if I have a multirec problem with my dual tuner setup(one Hauppauge 850 and one 950). I've been fighting intermittent recording failures for quite a while so I keep looking for any backend setting to try.