Editor doesn't work properly

[tranduyhung]

I have

Grav v1.5.5 Admin v1.8.14 Flex-Directory v2.0.1

When I add a new entry and I have a field as editor, the editor doesn't work properly. There is an "x" from nowhere shown in the editor, if you type something the content has a gray background. Here is a screenshot.

These problems don't happen to the editor for Grav pages or to any other places in Admin area.

Here is the content of my user/data/flex-directory/entries.yaml

title: Flex Directory
form:
  validation: loose

  fields:
    bookinfo:
        type: section
        title: Book Info
        underline: true
        fields:
            description:
                type: markdown
                label: description
                validate:
                    type: textarea
                autofocus: true