As mentioned by grisu48 in topic I can’t update the version Nextcloud 27.1.0 RC3 already, during the manual update in the CLI of version 27.0.6 to 27.0.7 the following error ocurred at the check for expected files:
xpp@Server:/var/www/nextcloud/updater$ sudo -u www-data php updater.phar
Nextcloud Updater - version: v26.0.0beta2-9-g64e2e4c dirty
Current version is 26.0.6.
Update to Nextcloud 26.0.7 available. (channel: "stable")
Following file will be downloaded automatically: https://download.nextcloud.com/server/releases/nextcloud-26.0.7.zip
Open changelog ↗
Steps that will be executed:
[ ] Check for expected files
[ ] Check for write permissions
[ ] Create backup
[ ] Downloading
[ ] Verify integrity
[ ] Extracting
[ ] Enable maintenance mode
[ ] Replace entry points
[ ] Delete old files
[ ] Move new files in place
[ ] Done
Start update? [y/N] Y
Info: Pressing Ctrl-C will finish the currently running step and then stops the updater.
[✘] Check for expected files failed
The following extra files have been found:
composer.lock
package-lock.json
composer.json
package.json
Update failed. To resume or retry just execute the updater again.
xpp@Server:
Once the four mentioned files are deleted, the update runs through without problems.
As far as I can see, these four files are standard files of the nextcloud program directory having the exact same time stamp as all other files in this directory! This is valid at least starting with version 27.0.6.
Somehow it seems the updater check files list is NOT updated. (Maybe that is why the Nextcloud Updater version is called dirty. 
)
