From what I’ve found, this happens on any error, including automatic handling of 404s, fetch requests that don’t return 200 and manually triggering notFound() in the page component. I’ve testet this up to 13.4.2 and it always leads to 500. It’s especially annoying because it’s impossible to debug what the underlying error is right now. You can try/catch yourself and avoid the problem, but it’s really not a solution.