EDIT: This post was previously titled "Links on REST services directory loop back to main directory page", but after researching, I have updated the title to be more indicative of the issue.
The main issues are:
1. Portal is now prompting users to log in to see any subdirectories in the REST services directory (it used to be publicly accessible), and
2. When I log in with a non-administrator account, I am stuck in a redirect loop where all of the subdirectory links take me back to the main directory. Built-in and Enterprise administrator accounts do not cause the same behavior.
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I have recently deployed Portal in our beta environment (10.7.1 - both Portal and Server). The hosting server's rest services page is here: https://castg.dep.state.fl.us/arcgis/rest/services
Any time I try to click any subdirectory links, I am redirected back to the parent directory page (the same one linked above):

I have seen this behavior before with this page, but it seems like it occurs intermittently. Now I'm unsure if it has ever been resolved, or if I've just assumed the problem was resolved because I'm able to use direct links to REST endpoints.