Legends of Runeterra targetting bug

I've encountered an issue where after my opponent has filled + buffed his board a lot, I couldn't target two middle minions (a lvl'd-up Karma and a Mighty Poro). In the same vein, when they casted Avalanche next turn, I've found myself unable to target with Deny either the original or the copied spell (an error message of "you cannot target that" appeared across the screen). I' have been encountering some unusal lag earlier that day, which might be related. Has anyone else encountered this?