Because I see this on the copy of your site but not on my test site (with the same plugins and theme) it leads me to think there is some possibly minor database corruption that may be responsible.
WPML includes several troubleshooting scans that can fix such issues, and I've been running those to see if they resolve the problem.
On my copy of your site, at WPML > Support > Troubleshooting when I ran the synchronize post taxonomies for the Posts post type (screenshot), that seemed to fix the problem.
Could you please try the same on your site and verify?
