http://domain/svg/filenotexisit.svg - file does not exist but passed with status 200 and app hangs

I'm not sure about your actual test URL, but I guess that URL also matches the expression in the rule, so it execute the rewrite action, which changes the response.

The URL you configured is /, which may point to some default pages (existing, such as index.html, default.html), so it returns 200. Please check it.

If I misunderstood something, please provide more details, such as a minimal example that reproduces the problem.