This may be a compatibility issue. Please try the following troubleshooting steps after a full site backup{mandatory} and make sure the bug exists or not.
1) Go to WPML>>Support page, click on the Troubleshooting link (blue link in the middle of the page)
2) On the Troubleshooting page, please click on the following options in the *Clean up* section. Wait for confirmation of processing after each one.
- Clear the cache in WPML
- Remove ghost entries from the translation tables
- Fix element_type collation
- Set language information
- Fix WPML tables collation
- Assign translation status to duplicated content
- Fix terms count
- Fix post type assignment
