Hello,
There might be some Cache issue (most probably) or some third party Plugin causing the conflict on your Site.
So, please once completely clear your browser and server cache and then check back the issue again.
If the issue persists, then please once try deactivating all the third party Plugins on your Site. If the issue gets resolved, then reactivate them one by one to see which Plugin is causing the issue.
If somehow issue still persists, then please take complete Backup of your Site first, then provide us the WP-ADMIN Login details of your Site in the Private Content field along with the permission to completely debug your Site which includes deactivating all the third party Plugins and removal of on-Site Customization changes too, so that we can thoroughly check this issue on your Site and assist you accordingly.
Best Regards