[Plugin: Scissors and Watermark] getting error: cannot update metadata

I am getting the same alert too!

Try the “regenerate the thumbnails” button. Worked for me, but doesn’t quite fix the problem.

OK so I found a work-around that has yet to fail.

Open scissors-watermark/functions.php and comment out ln1139 – 1155. So this function is no longer used:

// Check if exists files of custom sizes. If not we re-create all sizes including custom sizes.
		if ( !empty( $_wp_additional_image_sizes ) )
		{
			$custom_sizes = array_keys( $_wp_additional_image_sizes );

			if ( in_array( $_POST['target'], $custom_sizes ) ):
				 //	TODO: It re-create all sizes. It should to make only the custom size which miss
				$attachment_metadata = get_post_meta($post->ID, '_wp_attachment_metadata');
				$new_metadata = wp_generate_attachment_metadata( $post->ID, $fullfile );
				if ( !wp_update_attachment_metadata( $post->ID, $new_metadata ) ):
					return __('Can not update attachment metadata.', 'scissors');
				endif;
			endif;

		}

Whatever this was doing was failing, and since disabling it I have been able to use the plugin like expected.

Cheers!

@jamin84: Thanks!