So normally i used to do Gitlab via Docker in quick succession, but in Gitlab 14.1 Background Migrations were introduced. So You have to wait until the background migrations have finished to upgrade to the next version.
Unfortunately there is no shell command to see the background migrations. So you have to do the Admin Area
https://<your-gitlab-url>/admin/background_migrations
If you botched you install - like i did - and have no working interface, rollback to the latest working version - probably gitlab/gitlab-ce:14.1.7-ce.0 and wait until the background migrations finish.
This is necessary from version 14.1 onwards, so check the migration status in the backend before pulling a new docker image!