Well, I am also only having that issue from time to time. It didn't happen for some days now. I have 6.8.2 already running since 5 days. Maybe that solves the problem.
This issue can be marked as resolved. It was related to the time being off just ever so slightly. Re-synched my devices to NTP servers.
Managed to find another similar thread in the forum which pointed me in the right direction.
Thanks!