Hi Manuel,

when the 2 versions of sites desktop/mobile get mixed randomly usually is a problem of page cache. Issue for nonumber and admin tools are usually related to modules and other features.

If the siteground has a server side cache technology similar to the Joomla cache plugin probably that's the problem.
They need to disable it in order to ensure that dynamic switching will work as expected.

At the time of writing the only page cache plugin for Joomla that is intelligent to keep 2 separate cache for desktop and mobile seems to be JotCache.

Thanks and regards

John