Cards with Adventure from the Throne of Eldraine set used to work fine, but something in a recent patch must have broken them. Now, to cast the "Spell" side of an Adventure card, you need to have a free creature slot on the board - if you don't, it'll prompt you to select a creature to replace with your spell. If you say "Not Now", instead of just not casting the spell, the prompt will loop - asking you over and over which creature you want to replace until you finally select a creature to replace. If you select a creature to replace, that creature will die (as though it were being replaced by something) and the spell will cast and the creature slot on your board will be empty.
Here's a link to a short video showing this happening in the Fables of Eldraine event, against the Taste of Death enemy, where I couldn't cast Curry Favor (the spell side of the card Smitten Swordmaster) because all my creature slots were full. You'll see me tap "Not Now" several times to no effect, then eventually give up and replace my Smitten Swordmaster just so my turn can continue. The same bug also occurred with Swift End, which is the spell side of the card Murderous Rider.
Hello @Stormcrow ,
Thank you for all the information provided, this issue will be investigated!
If you have any additional information that you consider relevant, please don't hesitate to send me 😊