From what I can see it looks like maybe
– A missing file, try re-installing the plugin completely, to make sure it's not the case
– a 3rd party plugin or theme is loading/replacing/de-queing one of the scripts used, or something very similar to that. In this case I usually suggest disabling all plugins one by one and switching the theme temporarily, to see if it changes the situation. At some point the error should disappear, that will indicate that the last de-activated plugin is most likely the source of the conflict.
It could be something else as well, I have not seen such issue in a very long time. If the above suggestions not work, can you please fill temporary FTP and back-end login details, so I can check on the problem directly?Best,
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