mod_fcgid: error reading data from FastCGI server

Hi Heroes

we changed back from fpm to fcgi and are getting now the following error on all sites beside one site in all of our 4 Multisites - A bit strange as the site who shows up is actually not the root site and has also always a different IP. It also does not reflect the main domain.

Any ideas how to solve that problem are welcome.

Kind regards
Andi