Blender doesn't run my script unless blender crashes? I have the most unusual and frustrating issue at the moment. I've got a script, but I just can't get it to run. I've tried live edit, not live edit, using the run script button with and without the register check box. I've even tried starting a new blend file and importing everything as a proper add-on. None of them work. 

BUT, if for what ever reason, blender crashes, (which it is doing quite a lot at the moment... (I'm running the macOS Sierra beta which I probably shouldn't have done), then the script updates, and runs perfectly. It's just so impossible to use right now.
It sounds like you have a bug in your script.  Run blender from the command line, and it will tell you what the error is there.

Update: I found that node in your code in the beginning of it, you have a several lines that say s_slots[0].material.node_tree.nodes['S_R_MS'].inputs[0].default_value = 0.0
I suspect that is where the S_R_MS node is.