If you have any customizations, it might also be something in them, or something that got missed in a merge. It’s complaining because you still have the old component syntax somewhere:
{{markdown-editor text=model.area.summary}}
And it needs the new syntax:
<MarkdownEditor @text={{model.area.summary}} />
I searched the current webportal and extras code and can’t find any instances of markdown-editor, so I think it must be something specific to your game.