Failed to initialize plugin: sqc_embed_button

[petertwise]

Failed to initialize plugin: sqc_embed_button

This error appears sometime on wp-admin pages with no visible TinyMCE field like Pages listing or ACF > Field Group > [edit a field group with WYSIWYG fields]

It also appear on settings pages that do have TinyMCE fields like Theme Settings > Footer Text in the squarecandy base theme.