In a scene add an ActionManager to a mesh.
Register an action triggered by BABYLON.ActionManager.OnIntersectionEnterTrigger
serialize the scene
try to convert the serialized object to string
you will get the following error
"Line 46:28 - Converting circular structure to JSON"
see playground example
http://www.babylonjs-playground.com/#1UTZEV#10
if you comment out line 42
"sphere.actionManager.registerAction(action);"
then it works fine.
Please check