Multiple Logins session handling

Since grafana 3 we use multiple raspi/odroid machines to display dashboards in our office. since upgrade to garfana 6 (or from raspian to ubuntu arm with newer firefox, it was the same time) after a few hours only the last logged in raspi stays logged in, the other logins are expired.
Was there a change in the session handling with problems to make multiple logins?
Is it possible to configure this to allow peristant multiple logins with the same user from different ips.

I think this correlate with issue