Thank you. I updated your plugin and tried it. Unfortuneately, it did not resolve the issue with the progress bar functionality.
Lazy Load by WP Rocket allows the progess bar to function normally. It gives me a PageSpeed of 92% and YSlow Score of 77% (although I’m still building and optimizing the page, so the scores will get better). Of course, these scores would be even better with your plugin. When I deactivate Lazy Load by WP Rocket and activate your plugin, the PageSpeed score improves to 93% and the YSlow Score is unchanged at 77%. Your plugin does a beter job of optizimizing images and a much better job on Defer parsing of JavaScript (99% vs. 92%).
I haven’t had a chance yet to try your code. I’ll let you know the results when I do.
Regards