Special characters in slug

I create urls with date and slug like this:

post = “/:year/:month/:day/:slug”

In most posts there is no slug so it fallbacks to title. Now there are some slugs with special characters, mostly german umlauts (äöüÄÖÜ) and the sharp ß. I am not sure whether these urls are save in the internet. Can I somehow automatically convert them to ASCII characters?

I saw that if there is a period in the title the url is not found.
Maybe this is due to this bug: https://github.com/spf13/hugo/issues/1885