Okay…
My Provider had changed some settings so the automatic updates cannot be done anymore til I enter the FTP-dates (you know what I mean).
Today the Provider has changed the settings again, the update-downloads now can be done from the backend again and … wonder … the upload of the avatar pictures runs also.
At my side (veteres-unlimited.de) this side isn’t a multisite.
That some Avatars (existing ones like noordewier reports) would not be shown appears randomly, but no one can upload/change a avatar now.