Malastar's ability keeps prepping to one of his breaches! Why can't I prep it to another mage?

To prep a spell from the supply to a breach controlled by another mage, you must drag the spell directly to that mage's breach. If you click...

Why couldn't I choose which Mage takes their turn with the Paired Mage turn order option?

Normally, when a Paired Mage turn order card is drawn and neither Mage has taken a turn this round, you choose which one goes the first time...