Missing "standard" body classes

[Miroir Studio]

Hello,

my Magento website is missing the "default" body classes (for example "page-layout-1column").

That doesn't seem to be a theme related issue and I don't understand what is causing this problem. Where are thoose classes defined? Any idea of where should I search to find the cause of the problem?

[viktor_dmytruk]

In my case, it's module mailchimp 
https://github.com/mailchimp/mc-magento2/commit/a80240f9a6abdf6a4c9979070a2965c27eeba774
script tag not closed and body classes removed