all in the subject
I get this only HF-U, not on European sites.
At best, my request/update is just delayed 1 or 2 minutes (after sending it again), at worst it is lost.
Have seen a few replies below.
Now thinking of something not often done here : a full restart of my browser (not simply a restart of my PC).
edit : a full restart of the browser was not enough
a full delete of history was not enough
edit : maybe closing the tabs with the offending warning is the way...