Hi,
1. I found a possible issue with the configuration. I have turned off this option. Now it seems to be okay.
2. I can’t seem to replicate this though. Sounds like a FOUC issue. These are generally caused by lazy CSS loaders. Check if you have like cloudflare rocket loader for CSS or any other CSS lazy loader enabled. Those features should be used with care, and only if you can get the critical CSS to load first to prefent FOUC issues.