BTW Maybe another cookie related bug: If I log into the panel and then switch with Option + Command + R into Safari’s Responsive Design Mode and then do a reload, I am immediately logged out. Even on a fresh installation, even with @distantnative 's patch. So unfortunately if you want to debug something in the frontend with logged in users in Safari’s Responsive Design Mode – no chance.
I’ve checked with other web apps (Piwik, Harvest) for the same behaviour, but there I am staying logged-in. I googled briefly if Safari’s Responsive Design Mode is known for deleting / altering cookies but so far I found nothing.