The game let me cast Boltbend on an enemy counter-spell whilst there was only one other spell on the stack (the spell originally targeted by the counter-spell) and a large number of triggered abilities. This lead to a situation where I couldn't select a valid target, but the spell was already locked into the stack so there was no game action and we were forced to wait for the turn timer. My opponent conceded before I thought to get a screenshot. If it is relevant I had Queen Brahne, several of her Wizard tokens and a Copy of one made by Chandra, Flameshaper, Firebbrand archer, and a Firespitter Whelp.