Discover: "Error while submitting uselfulness"

Reading reviews and after trying to upvote, the whole Discover crashed first of all (!) and then after launching the store again and browsing where left only gives:

“Error while submitting usefulness: Error transferring - server replied:”

(there is nothing after the server replied). Also the attempted automatic bug report sending failed. There was a retry button that didn’t solve anything even after many many clicks.