UI events not sent from HTML/JS to client script

Events are not sent from the scripting API HTML via triggerEvent

scriptEngineHandle.triggerEvent("xxx"); <---
 

This can be reproduced by downloading https://aka.ms/minecraftscripting_turnbased & enabling the addon, creating a world & attempting to click the buttons to start the game. This is a major problem for scripting. I have attached the addon provided by Microsoft showing the issue.