All the info is here (https://github.com/Yoast/wordpress-seo/issues/6220) I opened a ticket to the folks at Yoast as assumed was an issue with their plugin.
If I disable the dashboard all is fine, enabled the shop pages on this site 500. If I disable Yoast and keep WPMUDev stuff on it works fine. But we need admins to have acces to Yoast, this seems to have happened post WP 4.7, but not 100% sure, we can grant access as required.
Note: This only affects logged in admins.