[Bug]: Web Updater’s "start update" button unreachable without scroll bar

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I am upgrading from v24 to v25.0.1 with the web updater. Due to the long list of apps being updated and the page disabling the scroll bar the button start update was unreachable.

I could successfully work around this by disabling the body { position: fixed } CSS style in the developer tools of my browser.

(disclaimer: I’ve confirmed that this issue affects the most recent Nextcloud Server because this is in an upgrade and I can’t possibly test the upgrade to a future version.)

Steps to reproduce

1. install version 24
2. start web update to version 25
3. click disable maintenance mode

Expected behavior

• list of apps being updated visible
• button start update visible and clickable

Installation method

Community Web installer on a VPS or web space

Operating system

Other

PHP engine version

PHP 8.1

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Updated to a major version (ex. 22.2.3 to 23.0.1)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

Enabled:
  - activity: 2.17.0
  - bruteforcesettings: 2.5.0
  - calendar: 4.1.0
  - circles: 25.0.0
  - cloud_federation_api: 1.8.0
  - comments: 1.15.0
  - contacts: 5.0.1
  - contactsinteraction: 1.6.0
  - dashboard: 7.5.0
  - dav: 1.24.0
  - federatedfilesharing: 1.15.0
  - federation: 1.15.0
  - files: 1.20.1
  - files_pdfviewer: 2.6.0
  - files_rightclick: 1.4.0
  - files_sharing: 1.17.0
  - files_trashbin: 1.15.0
  - files_versions: 1.18.0
  - firstrunwizard: 2.14.0
  - groupfolders: 13.1.0
  - logreader: 2.10.0
  - lookup_server_connector: 1.13.0
  - nextcloud_announcements: 1.14.0
  - notifications: 2.13.1
  - oauth2: 1.13.0
  - password_policy: 1.15.0
  - passwords: 2022.11.21
  - photos: 2.0.0
  - privacy: 1.9.0
  - provisioning_api: 1.15.0
  - recommendations: 1.4.0
  - related_resources: 1.0.3
  - richdocuments: 7.0.1
  - serverinfo: 1.15.0
  - settings: 1.7.0
  - sharebymail: 1.15.0
  - support: 1.8.0
  - survey_client: 1.13.0
  - systemtags: 1.15.0
  - text: 3.6.0
  - theming: 2.0.1
  - twofactor_backupcodes: 1.14.0
  - updatenotification: 1.15.0
  - user_status: 1.5.0
  - viewer: 1.9.0
  - weather_status: 1.5.0
  - workflowengine: 2.7.0
Disabled:
  - admin_audit
  - encryption
  - files_external
  - suspicious_login
  - twofactor_totp
  - user_ldap

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start by reproducing the web updater flow from version 24 to 25 and inspect the page after clicking “disable maintenance mode,” focusing on the body position rule and the app list layout. Verify that the app list remains visible and the “start update” button is reachable and clickable without disabling CSS in developer tools.