I experience the same problem When I try to counter a spell, and I get the dialog to "Choose target spell," I choose the spell and it still completes. Glad I'm not the only one experiencing this issue, but it extremely annoying.

I lost two games tonight due to "You find the Villains Lair" having this same bug.

Same thing happened to me three different times in two games. Negate was countering a destroy creature spell from my opponent and it asked "are you sure." Yes I don't want my creature to die, so i said yes. The next turn went the same way as I had another creature in hand. Maybe because it was a token creature created by a sorcery is what the most definite BUG was?

I had the same experience while trying to counter Sublime Epiphany with You Enter the Villain's Lair. Thus my previous spell was countered even though you're supposed to be able to counter a counterspell

I play a lot of UR spells decks. I've noticed for some time now that it doesn't allow you to counter spell your own instants. Part of my decks want to trigger prowess or fill the graveyard with instant/sorcery spells. So I'll cast an instant, and then I want to miscast or negate that instant, but it doesn't pause or let me or ask me if I want to do this. It just let's my first instant resolve. I know that 99% of the time you wouldn't want to counter your own spell, but for the decks I like to play, this is key.

I cannot target opponnent spells with my own counterspells, like Absorb or Dovin's Veto.
The game asks me if I am sure to target my spell, I answer "No" and try again to target opponnent spell but i still can't. The timer runs off and I lose the game.
It arrived 2 times today.

Yes, I experienced this same issue two or three times recently.
Using a instant counterspell it asks me to target the spell when it should automatically counter the (only) spell on the stack (and it failed to counter the spell) and I lost the game as a result :o(