Nginx with WordPress in Subdirectory

Hi guys,

I am running against a wall and really hope someone might help me out :-/
I am running 5 WordPress-Installations on my Server
4 directly in the httpdocs-directory and the 5th in a subdirectory, namely:
/var/www/vhosts/liesenfeld.de/httpdocs/WP

When I switch on nginx, the 4 WP-Pages will continue to work as expected, BUT the 5th in the subdirectory will not work anymore: doesn’t matter which page I click in the menu, it will always end up on the homepage. Like: I click on https://www.liesenfeld.de/dvd/ and it will jump back to https://www.liesenfeld.de
It is probably only something small, but I cannot find it ??

Greetings,
Dirk.