Moodle Update with Custom Plugins

I need to update Moodle from 5.0.4 to 5.1.1 using CPanel access. The automated update does not work.

Requirements:
- Provide CPanel access with username and password.
- Current setup has custom plugins and themes that need to be considered during the update.
- Experience with Moodle, CPanel, and handling custom plugins/themes is essential.
- Ensure that the update does not break any existing functionality.

Ideal Skills:
- Proficiency in Moodle administration
- Strong familiarity with CPanel
- Experience with custom plugins and themes on Moodle
- Problem-solving skills to manage update conflicts

Please ensure a smooth transition to the new version while maintaining the integrity of the custom elements.