I came across a situation when attempting a mystery that had a terror effect that spawned a monster.
The player had completed one of the tasks using the yellow die. On the next roll, the terror effect triggered, spawning a monster that was supposed to lock the yellow die.
We ruled that the since the yellow die was already used to complete a task, it didn't make sense to remove it to put it on the monster and cause the task to become incomplete again. Once the resolution phase was over, we then locked the die on to the monster card.
Was that the correct ruling?