Elvish Clancaller does not hold priority
How to reproduce the bug: Play a deck with elvish Elvish Clancaller in it. Have enough open mana to cast Elvish Clancaller or activate it's ability. Have no other priority holding play components (castable spells, etc.). Priority will not be held and phases will automatically progress, unless in full-control mode, as though you were unable to take an action. This often prevents casting Elvish Clancaller or activating Elvish Clancaller's ability.
Elvish Clancaller should hold priority when there are legal actions to take involving the card.