One of the websites we manage recently started having a problem with menu aliases containing "contact" as a substring: clicking the menu just brings up an empty page that just says "Temporarily Unavailable." This happened spontaneously, we didn't do any work on the website or update anything manually before this problem arose. After we found out about the issue we updated to Joomla 3.9.5 (this was a few weeks ago) but that didn't fix the problem.
I played around with different aliases, and found that as long as "contact" is a substring it will not work, but everything I tried without it was fine. Even "contac" and "ontact" work. It also doesn't have to be separated out with hyphens, something like "blcontactah" will cause the error. I tried adding "contact" to the aliases of the other menu items (not just the "Contact Us" page) and it broke those as well.
Does anyone have any idea for why this is happening?