Google Pagespeed Insights Error - "Largest Contentful Paint" test fails for "HTML5 webGL Standard"

Hi folks, I have some unusual errors in google pagespeed insights (and other tools) when testing a simple splash page that has been generated from within Adobe Animate 2020 argeting webGL standard (beta)

all tests from tools such as browsershot fail, not a single successful test.

It feels like an event isn't firing but I'm very new to Animate, 2 days. I'm not new to web building though and this is a very strange error. I haven't had a chance to investigate thorugly yet but posting here in case anyone has encountered this themselves.

Any help appreciated. The url for the test pages is

Original code generated from Animate  

Slightly modified code for asp.net core 3.1 environment  

Has also been tested in .net core 2.x with same results - errors

The animation itself works in all browser manually tested so far on mac, pc and several mobile devices - just no tools can measure it fully.

thanks in advance

Steve