This is likely the result of the Epic Status field. It can seem counterintuitive, but this is different from the regular Status field. To remove it from the Epic panel, you need to set the "Epic Status" field to Done, which can be done by expanding the options next to your Epic name in that panel (which appears to be the blue arrow in your screenshot). That should give you the option "Mark As Done", which will set the "Epic Status" field to Done and remove it from your epic panel.
An epic won't automatically show as done when all the issues within it are completed (by default). You'll still need to go into the epic and change the status to done.
You can use an automation rule to do set further epics to move to the done status once all issues it contains are completed. Go to project settings > automation and there should be a template automation rule you can set up.
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