Ok so as a workaround and just for info I am using this instead to replace to run scripts via ScriptEditor:
using System;
using Rhino;
using Rhino.Runtime.Code;
string scriptPath = "F:\\testrh.py";
string fileContent = System.IO.File.ReadAllText(scriptPath);
RhinoCode.RunScript(fileContent);
from the very insightful reply here by @eirannejad