I am finding that the classic editor is not rendering on edit pages since 5.6 the classic editor / tinyMCE seems to have been altered in 5.6.
However if you switch the editor to text mode then back to visual mode classic paragraph and classic editor blocks seem to be ok.
Here is a hack to do that after 2 seconds once the page loads.
jQuery( document ).ready(function() {
setTimeout(function(){
wp.data.dispatch( 'core/edit-post' ).switchEditorMode( 'text' );
wp.data.dispatch( 'core/edit-post' ).switchEditorMode( 'visual' );
}, 2000);
});
The issue seems to be that:
wp.oldEditor.initialize()
is no longer firing and many plugins/blocks looking for this event are no longer functioning.