The issue with not able to play in a CFM league if the league is at 31 members, if you are the 32nd person, you are not getting in, sounds like some overworked developer ( or a clueless junior dev more likely), forgot that indexing starts at 0, not 1. Somewhere that method that needs to count the number of members, for some other code to determine if the league is full, probably has the index set at 1 but its end number is 31, so instead of properly counting 32, its returning back 31 and that is incorrect causing all kinds of bad behavior. Because its only happening for coach only side, I'd guess this method is only called for certain areas, and the rest are using methods where the starting index was set properly(0-31).
Since I'm not familiar with their codebase at all. Just been in this field longer than I like to say, this issue that currently happens sounds very familiar, and how its manifesting itself to the users makes sense. However, sometimes the most simplest fixed , like this get missed. So my hope is someone just mentions this to the developers, and hopefully a bell goes off and they check, and change that index number to start with 0 not 1 so it can count league numbers properly and we can get back to our CFMs. As a commish, hearing the complaints is killing me, and yea we could try the workaround of starting our leagues over using the owners only, but that's not the mode most play CFM, for various reasons and no one likes to restart a league. So please, just mention this to them, take the credit for figuring it out. Maybe, if lucky they have some way to put in fix without waiting until their next patch drop.
If they already know this is what happened, and too embarrassed to say they let this code get past them during Code Review, get over it, * happens, just fix it, and just be thankful not a hard fix. Some developers may not even admit they made such a "dumb" mistake, and tell you some convoluted issue, to cover it up. But if its suddenly fixed, quickly, then we know what really cause it.