Just a quick note for anyone experiencing something similar.
We have a client who had a concern that /resources always redirected to /resources/. After a lot of wasted time checking the web.config for rewrite rules, writing rewrite rules that didn't work, disabling the 404handler, and testing init modules (routingOptions.UseTrailingSlash) Episerver's engineering team pointed us to the actual problem.
The site actually had a folder named Resources that contains the XML language files. After renaming the folder and updating the EPiServerFramework.config with the new path the URL worked without the redirect.
So long story short, if you are having a problem with an alias check to make sure that you don't have a folder with the same name.