Another tab is already working on this

This morning, I added a new admin user to the WP site, and when I logged in with the new admin user and began using UPFRONT I started seeing "Another tab is already working on this".

I've cleared all cache history on the browser. The problem persists. I've logged out of both users, the problem still persists.

Please remotely log in and see if it does the same for you. I have already granted Support Access.