What I expected to happen:
A custom spawner would be able to spawn hanging entities (such as ItemFrame and LeashKnot) in the world.

What actually happened:
Although the spawner appears to spawn (its particles go off), the entity does not appear anywhere in the world. This happens regardless of what its position, motion, rotation, and tile tags are set to - no combination makes the entity appear in the desired (or any) location.

Steps to Reproduce:

1. Import one of the attached schematics into your world.
2. Observe that, although an entity spins in the spawner cage, it's never spawned. This is the case even when its spawn particles (a burst of extra flames) go off.