The trade duration is not over, there is 2 and a half days remaining, I even got an alert message about that a couple of minutes ago (and the remaining time now shows in red).
I still get the “Confirm payment receipt” button on the “Open trades” tab, along with the message “Please send confirmation again” (is there a more detailed error log somewhere?). I click the button from time to time, only to get the spinning wheel (“Sending confirmation…”) stuck for a while.
As I said, I got my small seller deposit back, and I even transfered it to my external wallet. All my Bisq balances are now 0.
What I don’t get is how the buyer signed the funds/deposit transaction (as they have been released). The only explanation, as you say, must be that my fiat payment confirmation has actually be sent before, and all this is a pure GUI glitch. However it is an embarrassing one, as it throws doubt on the transaction for honest sellers (and buyers) that could not fully understand the nature of the bug.
I’m going to open a dispute just to really check if the funds were sent to the buyer.
By the way, I have spotted what the buyer’s real name is (from bank transfer information) and I have a way to get in touch with him on the Net. What is Bisq official stance on this kind of external communication?