Hi,
just for info, I just installed another Froxlor and this time I used Nginx again.
I used Apache2 first and later for the finally Froxlor installation I used Nginx with php-fpm
Everything went very smooth with now automatic configuration.
Today, all PHP FPM crashed. I found out, that the folder /var/run/nginx was missing.
So I created, as in previous Froxlor nginx installation, the folder /usr/lib/tmpfiles.d/nginx.conf
with the content
D /run/nginx 0755 froxlorlocal froxlorlocal
as its mention in
https://serverfault.com/questions/779634/create-a-directory-under-var-run-at-boot
all works now again and happy with Froxlor