At midnight, reality and the Spirit World completely overlap, and the mysticism's power fluctuates slightly. During this time, casting a spell makes it easy for you to attract the attention of some Spiritual Realm Creatures.
Although you yourself may not notice them, and they can't truly harm you, your situation is different. The spell you are casting is more sensitive than you are, and those Spiritual Realm Creatures can play some small pranks on your spell.
The eventual result is that your spellcasting fails.
Of course, this influence is not severe; it's just a bit annoying in the novice stage. Once you master a spell proficiently, this effect can be almost ignored, and generally, Spiritual Realm Creatures don't dare to mess with witches, whereas other mortal races might be frequently harassed.
It is precisely because of this setting that Dorothy can verify whether her suspicion about the world's layers is true or not at this time.
