Local database
If something went wrong and you would like us to see it, this sends the record above — and only that record — now. It is the one thing here that is sent because you chose to: if your browser asks us not to measure you we honour that everywhere else, including for faults.
Break this tab on purpose
Each of these makes this page fail for real, in a different way, so that what happens next can be looked at. Nothing is destroyed and nothing is sent to anybody else: reload the page and it works again.
Afterwards, look at the boot timeline above for the line it added, and at what would be sent for the record it produced.
Make the browser database go quiet
This is the fault that prompted all of the above: a browser database that accepts a request and never answers. It cannot be caused on this page, because the database is opened before this page exists — so it takes effect the next time you load the site, in this tab only, and stops when you close the tab.