This is very sporadic, and I am not sure how to reliably reproduce it. Once in a while, when I play a card combo that allows me to knock out an agent and am prompted by the game to do so, the opposing players agents aren't clickable. I have had a similar bug occasionally with drawing cards, selecting free cards, or other actions that require card clicks when prompted by the game. The only option is to end the turn, or to forfeit the game.
I'm playing on a PC with windows 11, and all my drivers are updated.