Hello, Ministry Of Concrete,
Even with the Xstore Core plugin disabled, the error persists.
We are currently seeing that the issue is caused by the plugin sitepress-multilingual-cms, please refer to the screenshot below:
https://prnt.sc/0rC8UENKq6mO
Please try to disable third-party plugins and check if the issue persists with a default WordPress theme too.
Kind Regards,
8theme team