hese three cards combo triggers an interface bug/error (see images)

Encroaching Mycosynth
Nexus of Becoming
Frostcliff Siege

1. Encroaching Mycosynth turns all nonland permanent to artifacts.
2. Nexus of Becoming lets exile a creature or artifact from hand at beginning of combat then makes a 3/3 golem artifact creature token thats a copy of exiled card.
3. Frostcliff Siege. This card enter whit Jeskai or Temur mode, that user must select.

The interface error becomes in step 3. When i have to select Jeskai or Temur. Giving “missing Promt #(numbers)” instead of “Jeskai” or “Temur”