I'm also getting an error when running the Subframe Selector. "Graph Error: Invalid script execution"
This was happening intermittently with 1.8.6, and now almost always with the 1.8.6 bug-fix release. I've updated to the latest Subframe Selector just now and it happens with that as well.
My use-case is that I run a remote desktop onto a Windows 10 machine from my laptop to run PI.
I did manage to get the Subframe Selector graph running today by running PI with --opengl=software. However it's not working now and I don't know if that is because I've since updated to the latest Subframe Selector or whether it was just coincidence.
My initial work-around was to plug a monitor and keyboard into the windows 10 machine, start PI and then connect via remote desktop. This always worked.
The other work-around I've found is to save a project with a working Subframe Selector in it. If I load that project, the sub-frame selector works, regardless of what options I start PI with.
I just tried launching it from the process-explorer as suggested by fmeschia and that works for me as well! That gives me a solution for now.