1.- Could you tell me if the issue persists with WPML plugins deactivated?
2.- If the answer for the step above is true, I would like to ask you to follow this steps in order to isolate the cause of the issue:
- Back up your site first before making any change, this is for security reasons.
- Deactivate all the plugins that are not related to WPML.
- Switch for a moment to a WordPress default theme like Twenty Seventeen.
- If the issue is gone, activate one by one to see with which one there is an interaction issue.