500 Internal Server Error

As the topic says, I am getting the error 500 Internal Server Error in my browser after trying to refresh.

I was browsing some movies in my list. When scrolling down, suddenly, movie artwork stops loading. So I hit refresh. At which point the page fails to load and I get that error.
I RDC into the home server, and pull up Plex there, and same thing. This is the second time it’s happened, where the solution seems to be exiting the program and restarting.

Any ideas?