My immediate thought was this must be a legal issue based on DSP using the words, a party taking action against him. But the more I consider this, I don't think this makes sense. You typically don't get warning of a potential lawsuit, people don't warn you about this they just file the suit and you get served.
Curse dropping him seems plausible, maybe Curse is actually being nice and saying hey this may happen because of the rule changes so heads up. My issue with this one though is, if Curse was doing this it probably would not just be DSP being dropped. If they warned DSP they probably warned others and I think the youtube drama world would have found out about this and we would see more discussion about this pending curse action.
I'm leaning more towards credit/loan issues. DSP has stated he can't get more credit, implying he has tried so he probably has quite a few hard inquiries over the past two years. It is possible the State taxes he owed got reported to credit agencies, and if this happened it is probably a huge negative mark. He has said in the past he used credit cards to pay his federal estimated tax payments but cannot anymore because he has no credit left, so his credit utilization must be really high. All these factors could really be hitting that credit score.
From what I can tell its very hard, maybe impossible for a bank to call in a mortgage unless the payments are missed, in particular on a primary residence. There might be a chance the CT loan could be called, but I'm putting that one at low risk. I think what could be more likely is credit cards could be getting their limits lowered. This would force him to either pay down below the new limit right away or face some penalties, higher interest rates all of that bad stuff. His credit card debt could quickly spiral out of control if this happened. Other potential is if he was able to ever take a HELOC out on either house, that apparently is much easier to call in versus the mortgage. I know at some point he has mentioned "business" loans in the past, who knows what these could be or if they really even exist in the sense of what a business loan is. If they do exist those could be in play.
If it is the credit/loan issue, you mix that in with the fact that he has paid nothing towards his 2018 Federal income tax and things could get real bad, real fast for DSP and chapter 13 BK starts to look like the right answer.