@Substring I will gather together what the information regarding what I've changed and we can discuss. I didn't take notes as I went along so I'll need to work backwards. I don't actually think I changed too much though.
As an aside, I took a look at S94manager and I see that it also uses the API in some instances (for example launching a ROM), so some of those things are also broken in 4.1.
I've being playing around with the API node module and it runs on 4.1 directly as a node process with just a few minor fixes to to the solfegejs node module.
I am going to patch S95api to start this process without PM2. If you'd like me to share the changes I'm happy to do so.