Dashboard hangs but cluster status shows 'Ready'

I installed two nodes and did not create any clusters or VM’s on it yet, but let it run for a few hours. Now the console shows the cluster URL and the status ‘Ready’ in green after entering (F12) and exiting the console, but the dashboard has become completely unresponsive.
I can still SSH into the hosts.

I looked in /var/log but could not identify any readable/usable logfile, like syslog or messages (I’m familiar with Debian…). How can I troubleshoot these systems?