Issue for query parameter in the url

Hi All
on multisite installation we are facing up a problem with query parameters inside the url.

This problem is affecting only the principal site of multisite network (more then 50 subdomain with different url).

One of this url, in the main site,
that doesn’t work is :

https://www.italiani.it/ricerca-network-italiani?q=birra

Another examples of this problem is
during registration of users : you can try to login as subscriber on

https://www.italiani.it/area-utenti-italiani (doesn’t work)

but on subdomain

parigi.italiani.it/area-utenti-italiani (work)

Can you help us why this is affecting only the main site ?

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