Rank Math Problems with german Umlauts

For one of my post with a Focus Keywords with german Umlaut ü = “ü” Plugin did not work. It shows “SEO: Not available”.

URL: https://o2.surfen-telefonieren.de/o2-homespot/o2-homespot-verfuegbarkeit

Screenshot 1 with Focus Keyword: https://o2.surfen-telefonieren.de/inhalte/2020/02/bug1.png

Screenshot 3 – not Work: https://o2.surfen-telefonieren.de/inhalte/2020/02/bug2.png

When i change Focus Keywords too only “o2 HomeSpot” and save post it works. After changing back to “o2 HomeSpot Verfügbarkeit” it did not work again.

I hope you will find a solution for Umlauts, because i spend long time for migrate vom wpSEO to Rank Math and still have many other blogs i want to use Rank Math – but with this bug i have to search for another plugin.

If you will fix the problem URL Check should include ü = ue – than means, wenn Focus Keyword is Verfügbarkeit URL will be …verfuegbarkeit and this is fine in SEO for Google.

Thanks a lot!

The page I need help with: [log in to see the link]