Thank you for the tip, I’ll check it out, if the Pi runs unstable again. Just surprised, it sounds that it happened often to you… Since I upgraded to better sd-cards, I never had sd-card trouble again for nearly a decade now. (And I am constantly running multiple Pis 24/7 as servers)

Thanks. I could neither find a file /var/log/kern.log nor did find /var/log | grep -i mess have a match.

dmesg and journalctl -k, found only entries after reboot, that the shutdown was not clean. Any specific logs where I could find more?