You need to add debug messages to all events. You will be able to see which events are firing and when, monitor variable values etc.
Simply add Browser Log to critical events, then run the game, open browser console (F12) and check the logs.
For example, add this to all AJAX On Completed:
Browser Log "Tag: " & AJAX.Tag & ", Data: " & AJAX.LastData
Create AJAX On Error event and also add:
Browser Log AJAX.Tag & " FAILED!"
Add this to the beginning of the function:
Browser Log Browser.URL ", " & URL_GameVersion
You will find the problem in no time.