After update to NC 28 the web UI updater stucks in step "Delete old files"

I’m experiencing a problem with the web UI updater after upgrading from v27 to v28. Since v28 I will always get stuck in the last step in the updating process.
All upgrade steps from “Check for expected files” (step 1)" to until “Delete old files” (step 9) are fine but the last step “Move files in place” (step 10) always ends with 404.
‘Retry update’ does not work since the same (invalid) request is sent again.

I made some investigations and found at least two work around for my problem:

  1. with Firefox’s Edit and Resend option append
    ‘index.php’ to ‘step=10’ request ‘POST https://nc-docker-server/cloud/updater/

  2. continue update from commandline (the stucked web UI update process will go on normally):

    cd /var/www/nextcloud/
    su -c “php updater/updater.phar --no-interaction” www-data

The web UI updater behavior seems to be a little bit suspicious since the requests steps 1 one 9 with the same request URL work but with data ‘step=10’ it fails.
The interim request ‘POST https://nc-docker-server/cloud/updater/index.php’ with result 200 obviously breaks something so a succeeding (original) request ‘POST https://nc-docker-server/cloud/updater/’ does succeed now although it was failing before.
Neither the nextcloud.log nor the updater.log show any error.

Am I the only one who has this problem at update step 10 ?