Sorting in admin not working in 1 of specific site

Hi,

I have tens of websites that use this plugin, and used it for many years, but 1 site seems to give me issues all of a sudden. It’s working on my local installation but the dev and production servers are having issues. There is no custom code regarding this plugin in de functions.php and it already happens on the default ‘page’ post type. I’ve also ‘Reset Sorting’ for the page overview and after that turned off any possible conflicting plugins, with no succes. Maybe I can create an admin on the dev server so you can check? (please don’t deactivate the caching plugin, it breaks the admin)

One thing I see is that the element with id ‘the-list’ doesn’t get the ‘ui-sortable’ class. There aren’t any errors in the console though. Switching to a default theme didn’t help either. I don’t know where to look any further.

Thanks in advance!
Tom