In Rhino there are different ways to edit materials/environments, and handling these from the plugin is bit different (dependent on the actual mode), which causes problem here.
Normally in case the user edits the Custom Material from the Material panel. In this case every change happens instantly. But it is also possible to edit the material from a Modal Dialog (for example “Layer Material”) and in this case only after the user clicks on the OK button should the plugin accept the new values, but from the Eto Collapsible form it is not visible. I mean the plugin has no idea about the mode the material is edited and how to handle the change. (Also it knows nothing about what button the user clocks at the and - OK or Cancel).
What is the correct way to handle it? Maybe I could try to investigate what kind if dialog is on the top, and this could be a sign for the plugin how to handle changes, but it is a bit messy solution.