Page is hidden at first causing a `visibilitychange` event during testing

Good Day,

PSI (i.e., Lighthouse) yields inconsistent results every time we run it. Why? DebugBear and WebPageTest are consistent all the time.

Specifically:

(1) Sometimes, PSI detects Google third-party files such as googletagmanager.com, analytics.google.com, or ads.google.com although we have properly delayed those files. Sometimes, they are not detected - which is the expected result. Details: https://prnt.sc/lrtXbIhHQFLq

(2) Sometimes, PSI detects CSS files that we have properly omitted from loading via RUCSS or Async methods. Sometimes, they are not detected - which is the expected result. Details: https://prnt.sc/N3sekB7-epen

**Noteworthy:** The waterfall results displayed by WebPageTest are correct and consistent every time and serve as our indicator to determine our site's performance and payload. By comparison, the results displayed by PSI are not so we cannot rely on it anymore. We have cleared all cache and allowed our cache to build over a period 3-5 days to ensure all pages load the same way, yet we still get inconsistent results with PSI.

Bottom line, why is PSI so inconsistent in its results? Can you kindly look into this and fix this condition? What did we miss? 100% sure that if you run any site with PSI these days, you will notice the same behavior with those sites.

Help appreciated. Thank you!