Thank you for your help!
Fixed with a manual fscheck; system updated to 18.04.20 successfully and seems to be stable.
I'll keep an eye on the sdcard, but for now everything looks fine.
Thread can be closed, have a nice evening everyone!

@oyyodams Its a Transcend Extreme-Speed Micro SDHC 32GB Class 10 card.

That's quite strange; everything else seems to work just fine. Could this be caused by overwriting the card with Etcher? I had a 4.x Dev Branch on it before that was no longer updateable so I've decided to reinstall.

Do you think this could be fixed by a manual umount / fscheck?

Thank you!

Support file was uploaded to
https://www84.zippyshare.com/v/QyFW7wZz/file.html

Hello everyone,

I am running a 18.03.30 on my Raspberry Pi 3b and now I get a notification that a new version (18.04.20) is available.
Wenn I start the update, the new version seems to download just fine (244 MB as far as I remember).
After that the system is restarted to install the new version.
This however seems to fail;
the system boots to the Recalbox Intro Screen, then suddenly reboots again and loads the
old version 18.03.30.
I have about 16 Gig free space on my card, so that should not be an issue.
Is there an update log file I can check if there are any errors? How can I help to identify the problem?
I tried to find if there are other people who have this issue, but unfortunally was not able to find a similar problem.

Thanks!
Stefan