You could have added such relevant info as your Sketchup version.
The wording “default browser” does not really describe it well. What SketchUp versions before 2017 were using is the operating system’s included browser engine (totally independent from user preference). SketchUp 2017 and later bring their own browser engine based on Chromium, so it is not influenced anymore by the operating system’s settings, versions and bugs or the environment outside SketchUp.
Sorry, I’m asking myself the same because I did not yet really understand your question. Can you rewrite the relevant question in a short and structured way?
Have you tried clearing the browser cache?
Windows: C:\Users\<username>\AppData\Roaming\SketchUp\SketchUp 2018\WebCache
macOS: /Users/<username>/Library/Application Support/SketchUp 2018/WebCache