This seems related to Invalid CSRF token errro in 1.6.1 while going to query/stack trace tabs · Issue #258 · temporalio/web · GitHub. I am using v1.6.2. This error is raised when I tried to terminate an activity, but otherwise the UI appears fine. Clearing the csfr-token fixed it – a new one was issued by the UI.
Let me know if you prefer a new issue or re-open the existing one.