[solved] 'Path not found' after migration to new Server

Hi,
I had to relocate my NC 20 to a different machine and now have some trouble with the paths. Maybe someone sees the blind spot I’m missing?

Both machines run on Debian Buster, with Nginx, MariaDB, PHP7.4 and Redis configured properly. NC is installed on both machines follwing the Howto I found here
In order to migrate I put NC in maintenance mode on the old machine, tar’ed the relevant directories and did a mysqldump (as described in the official migration docs). Copied all of these to the new machine, put them to the correct locations and double checked the permissions. After that I disabled maintenance mode and was good to go - I thought.
Someone hinted to rescan all files with
sudo -u www-data php occ files:scan --all
and so I did - here’s the result:

Starting scan for user 1 out of 7 (admin)
Starting scan for user 2 out of 7 (user1)
Path not found: /user1
Starting scan for user 3 out of 7 (user2)
Path not found: /user2
Starting scan for user 4 out of 7 (user3)
Path not found: /user3
Starting scan for user 5 out of 7 (user4)
Path not found: /user4
Starting scan for user 6 out of 7 (user5)
Path not found: /user5
Starting scan for user 7 out of 7 (user6)
Path not found: /user6
+---------+-------+--------------+
| Folders | Files | Elapsed time |
+---------+-------+--------------+
| 290     | 11831 | 00:00:03     |
+---------+-------+--------------+

And true to the error I can’t access my files - except for when logged in as admin.
All dirs on the disks are owned by www-data, MariaDB uses utf8mb4 as charset for the DBs and neither Nginx nor PHP shows errors.
The NC log is getting filled with entries like this:

{"reqId":"6FFsR1ZT58BdMtfvqfNu","level":0,"time":"2021-01-05T08:27:52+01:00","remoteAddr":"94.134.15.181","user":"user2","app":"scss_cacher","method":"GET","url":"/apps/dashboard/","message":"SCSSCacher::process ordinary check follows","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36","version":"20.0.4.0"}
{"reqId":"6FFsR1ZT58BdMtfvqfNu","level":0,"time":"2021-01-05T08:27:52+01:00","remoteAddr":"94.134.15.181","user":"user2","app":"scss_cacher","method":"GET","url":"/apps/dashboard/","message":"SCSSCacher::process ordinary check follows","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36","version":"20.0.4.0"}
{"reqId":"6FFsR1ZT58BdMtfvqfNu","level":0,"time":"2021-01-05T08:27:52+01:00","remoteAddr":"94.134.15.181","user":"user2","app":"scss_cacher","method":"GET","url":"/apps/dashboard/","message":"SCSSCacher::isCached d149-ea2e-dashboard.css isCachedCache is expired or unset","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36","version":"20.0.4.0"}

I’m lost for now. Any hints how to solve this?

Crap - now it works, and I didn’t do anything …
The log has these entries:

{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Finished OCA\\ContactsInteraction\\BackgroundJob\\CleanupJob job with ID 22072 in 0 seconds","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Run OCA\\Talk\\BackgroundJob\\ExpireSignalingMessage job with ID 90","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Finished OCA\\Talk\\BackgroundJob\\ExpireSignalingMessage job with ID 90 in 0 seconds","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Run OCA\\Talk\\BackgroundJob\\RemoveEmptyRooms job with ID 91","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Finished OCA\\Talk\\BackgroundJob\\RemoveEmptyRooms job with ID 91 in 0 seconds","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Run OCA\\UserStatus\\BackgroundJob\\ClearOldStatusesBackgroundJob job with ID 22149","userAgent":"--","version":"20.0.4.0"}
{"reqId":"NxTMBHv66xpsOwjmjZZC","level":0,"time":"2021-01-05T08:35:02+01:00","remoteAddr":"","user":"--","app":"cron","method":"","url":"--","message":"Finished OCA\\UserStatus\\BackgroundJob\\ClearOldStatusesBackgroundJob job with ID 22149 in 0 seconds","userAgent":"--","version":"20.0.4.0"}

Sounds like a background job did the trick, but I really don’t know why it didn’t earlier, since the server is running for a few days already (didn’t have time to do everything in straight followup).

So - problem solved, but knowledge hasn’t been gained.