Recently I have the problem that visits break up into several visits and are then counted multiple times in the stats.
See the attachted example. Piwik recognizes the page views (which are within seconds/minutes) as coming from the same visitor but counts them as separate visits.
can you try upgrade to our latest 2.16.0 beta version? this issue may be fixed. If you still experience it (after upgrading and you find new data still is buggy), please create a bug report @ Issues · matomo-org/piwik · GitHub
Now my dashboard is broken (empty), All I see, is the menu on the left and the top. None of the reports is loading. And I can’t step back to 2.15 because the database got upgraded.