Got an error 500 the other day when trying to visit /m/theonion@midwest.social, what was strange was that it was not rendered "within" the context of site UI but I was shown a totally white page bereft of any decorations except the error message on the top left (first time I ever saw this).
Got an error 500 just now from replying to a message, it was a typical error 500 taking up the main body column on the site (appeared to be logged out and all), and then returned to normal after refreshing.
EDIT: Just tried out spoiler syntax for the first time to update a new thread and submitting the edit also gave me a regular error 500. Edit didn't go through and I had to go back to resubmit.