Resource types

I find that for some users, some images (when called by the main file in the file resource type) don't display some of the time.  My theory is that if the content in the file resource takes too long to load, then only some of the files will get loaded.  What I'm wondering though is if anyone knows how this process works "under the hood."  I haven't had time to look at the core code for this yet; I'm just trying to get some general idea of how to troubleshoot this issue.  Our goal is that when using a file resource, all users get all the content all of the time, without having to refresh or try again later for it to show up.  Any ideas on how to get to the bottom of this would be appreciated.  Thanks.