And the available space on the /tmp dir is 980 Gigs.
I wonder what it was at the time of the fill? Do you have either a large backup or a large Remote volume size on the Options screen (default is 50 MB). Is error-named file still there? How big?
For the XSRF popup, if usual browser reload doesn’t help, try a hard refresh, sometimes Ctrl-F5,
but it varies by browser. There are directions for the popular browsers, findable with web search.