Short code not working

I get the same issue, though with a bit of poking around in FF developer tools Network, I can see the issue causing the update failure.

The following is being output before the expected json response when the publish button is clicked:

<style>
.rpwe-block ul{list-style:none!important; ...
</style>

This is generated from
function rpwe_custom_styles()
which is called from
function rpwe_get_recent_posts( $args = array() )

My fix was to comment out the call to generate the custom styles:

	// Display the default style of the plugin.
	if ( $args['styles_default'] === true ) {
//		rpwe_custom_styles();
	}

This also means that the front end formatting will not now have the rpwe formatting applied as the css is not being output.

What the correct solution is I don’t know, I don’t understand enough about WP.
But it get’s me out of a hole!