Thanks for the link @mreach. I’m not seeing any obvious issues from here.
You mentioned that this is only affecting one user on the site. Do you know if it’s a problem is limited to a single browser/device? Or does it happen to this user even when they log in using a different device?
If it’s just one browser/device, then it could suggest a browser plugin (e.g. an ad blocker) intefering with Discourse’s code.
If it’s affecting them in every browser, then that’s more tricky. Do you have any third-party plugins installed on your forum? It would also be interesting to know what the user has configured for their ‘default home page’ (found in their Discourse ‘interface’ preferences)