Generally, when you pick multiple instances by UID, you need to use "For Each".
So change your code to this:
.
Also, if you only have a few enemy types, it may be easier to combine them into two sprites. (combine art1, art2, art3 into one "art" sprite, and base1, base2, base3 into "base" sprite)
This way you will not need to use families and you'll be able to fully benefit from the use of the container. You will no longer need the baseUID variable as instances in containers are picked automatically.
Of course you will have to add another variable "EnemyType" and name your animations like "Walk1", "Walk2", "Walk3" for different enemy types.
So your events may look like this:
Base Platform is jumping -> Art set animation to "Jump"&Art.EnemyType