Icon meta box not updating when changing json

So I have an MB Blocks custom block with in it an Icon field. It's defined something like this:

[
				'type' => 'icon',
				'id'   => 'custom_icon',
				'name' => 'Icon',
        'icon_file' => get_theme_file_path('includes/icons.json'),
			],

Now, when I add an icon to the icons.json file, it does not show up in the editor when I try to change it.
Of course, I've tried refreshing and clearing caches but nothing seems to work.

What could cause this issue?