Can't click in additional Editor fields

I'm seeing an odd issue where it's not possible to click into extra editor fields. When clicking to focus the cursor, nothing happens, though occasionally a right click will focus the cursor.

The site has been live for around a year and this has only just started working.
It's happening in latest Chrome on Mac OS Sierra and latest Edge on Windows 10. There aren't any console errors.

The field is set up like this:

header.blocks:
  type: list
  label: Sections
  style: vertical
  fields:
    .body:
      type: markdown
      label: Section content
      showPreview: true
      validate:
        type: textarea

I realised this was out of date, so have changed it to this, but the issue is still there.

header.blocks:
      type: list
      label: Sections
      style: vertical
      fields:
        .body:
          type: editor
          label: Section content
          autofocus: true
          lint: true

Has anyone else experienced this?

Thanks!

@tomatso

here is an open issue about

https://github.com/getgrav/grav-plugin-admin/issues/1168