Hi,
I'm having an issue when the WP Smush plugin in active. Wordpress registers that the image has been uploaded but the thumbnail is a broken image. Also I get this error in the logs:
KILLED QUERY (23374 characters long generated in /nas/content/staging/abtrogers/wp-content/plugins/wp-smush-pro/lib/class-wp-smush-stats.php:75): SELECT post_id, meta_key, meta_value FROM rgrs_postmeta WHERE post_id IN (17420,79,17438,108,17439,109,17440,110,17432,111,13615,112,17434,113,17441,114,17425,........(etc..)
Edit: This seems to happen only when the WPML Multilingual CMS plugin is active