Permalink – strange behaviour

Hi all,

I have a strange behaviour regarding the permalink/URL when navigating to a product. My side is about selling royalty free music to customers and it its vital to provide a permanent link e.g for advertising.

SO here is the problem:
Description: I want to link to a new album eg.:
https://hartwigmedia.com/gemafreie-musik/alben/lazernoid/back-in-time/

CASE 1: Registered and Logged in User
The link is shown correctly when I am a logged in user. That´s fine

CASE 2: Not registered User
In that case the link is immediately “rewritten” e.g with
https://hartwigmedia.com/musikshop-gemafrei/genre/pop/the-days/

That´s one of the product of the album (category).

I already disabled my plugins but the same behaviour is shown. So I am really confused and need some pro advice from you guys!

The htaccess looks like:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

So nothing fancy here too…some ideas?

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