System notifications says I'm currently editing a page in another window - but I'm not

[gornycreative]

So for some reason I regularly get the warning that a page I am working on is being edited in another window and that I started editing that version the last time I opened the page. So it will be a few minutes off usually. I also noticed that it took a lot of massaging to get the timezone it was showing to match the timezone on the server and the times on the site. All looks good in php_info and the site config file in terms of the set timezone.

No one else is editing, I've got no other open tabs with the page editor on. Any idea what could be causing it? I will likely just turn the feature off for now, but it only started recently.