Automated upgrade to 12.0.1

I’ve mentioned almost the same questions over internets, but could not find a workaround.

I was trying to migrate from 11.0.3 to 12.0.1 using built-in updater. I was never forcing nextcloud to migrate, it merely asked me to migrate as it was happening several times. And there were no any fails.

I’ve started the migrate process. It said it was ok, then it pointed me to the index page to make the update completed. But the “Start update” button can not be clicked. The script /js/core/merged-template-prepend.js could not be found.

Main page pic:
Google Chrome console pic:

Nextcloud version: 12.0.1 (?)
Ubuntu 16.04
Apache 2.4.18
PHP version: 7.0.22
Is this the first time you’ve seen this error?: Yes

Topic should be closed. The problem has been solved eventually by myself.