I know this question is old, but I have been playing around with this and here are some thoughts. It may be a good approach to leave the Donwload non-HTML resources option enabled and leave the EXTRARES as-is. If you are getting http-404 resources not found, it could be due to changed images/js/etc. files. In that case you could probably leave the Download non-HTML resources option enabled and comment out the EXTRARES. I did many tests and include some of the images here. My consensus is that:
When you have the following option checked, it will automatically grab the latest EXTRARES
'Run -Time Settings' > 'Browser Emulation' > 'Download non-HTML resources'
