The fix for this bug causes a new user agent to not be applied if a website is currently loading. Domain settings are set before the load begins, so if a website has a domain specified user agent, it will be applied before the load begins. But if the website then redirects to a URL that has specified a different user agent, this second user agent will not be applied. Also, if the user presses back while a website is loading, the user agent of the loading website will still be applied irrespective of the specified user agent of the website that is being returned to.
The fixes for these problems would be complex because of deficiencies in the controls provided by Android’s `WebView`. After the website finishes the correct user agent could be applied, but tracking that would be complex. Alternately, we could apply the user agent on every page finish (there might be some bugs to doing this, I haven’t looked at it closely enough). In either case, in the above scenarios, the web server would see a connection from one user agent and then a second connection from the other user agent, which isn’t a real good solution.
A permanent solution after the fork of Privacy WebView would be to modify `WebView’s` behavior to make it more intelligent about switching user agents when loading websites, but those types of changes would be deep and require a lot of maintenance. I’m not sure it would be worth the effort.