There is a bug with Structure Block that upon loading the saved structure will keep spawning saved entities.

Steps to Reproduce:
[Step 1] Save a structure that includes entities. Settings: Include Entities - Include.
[Step 2] Load that structure with settings:
Include Entities - Include
Remove Blocks - Remove
Animation Mode - Place by Layer or Place by Block
Animation Time - any number greater than 0.

Observed Results:
The structure block will keep rapidly spawning the saved entities and cannot be stopped.

Expected Results:
The structure block should spawn only one entity for every entity in the saved structure.

Notes:
Picture 1 shows the saved structure.
Picture 2 shows the expected result.
Picture 3 shows the current result.

The bug spawns so many entities that the world will immediately start to lag and the lag will worsen over time.