What is wrong with this premise?

[Jenny A]

Premise: Everything that has come into existence has had a cause.

What is wrong with the above premise?

Depends upon what is meant by come into existence. From your example of The Harry Potter movie and crystals, you already appear to have several meanings for coming into existence.

In the case of the Harry Potter movie, what we are talking about ultimately is a group idea made audible and visual by technology. It isn't a DVD, just copied on one and there is no original in any real sense. In fact as an object you could, and I do argue that the Harry Potter movie doesn't exist at all, certainly not physically. But DVD's of it do each individually exist, as do various copies on computers and elsewhere.

It would be very hard to put a finger on when and how the idea came into existence. When the screen writer wrote it? After it was filmed? After the editing? On distribution? When?

This is a problem with novels too. Moby Dick exists in a way, but you can't touch it, or show it to anyone. An orally transmitted song or poem is even harder to pin down.

Just defining the existence of an idea is problematic.

In the case of crystals you appear to mean there is something that caused every object's atoms to arranged in the particular form that they are now in. And we do see lots of atom rearranging going on in the world, and generally it has a cause, whether it's heat melting ice, or a river rounding a stone, or a organism formed at the direction of DNA.

The problem with this type of definition is that it's hard to put a finger on when something new came into existence or whether it stays the same thing over time.

I am the product of a sperm cell meeting an egg. But I've changed rather a lot since then and I probably don't have any of the same atoms anymore. And much of my body is friendly bacteria and other things not directed by my DNA, but having DNA and separate causes of their own. And much more than DNA was necessary to build and maintain me: a uterus, an umbilical cord, blood containing nourishment and oxygen, my mother's immune system and so on. And then more food, not to mention shelter and protection was necessary to allow me to grow and to maintain me. At what point did middle age Jenny come into existence?

A very old example of this problem is a ship that is repaired over time until none of the original material is left. Is it the same ship? And what is the cause of the ship? The growth of the wood to build it and the weaving of the cloth for the sames, and winding of the rope to hold them? Or is it the builders, or the designer, or those that payed for it, and is repairing it a cause of it's continued existence?

Existence is still a pretty loosey goosey thing defined by this kind of example. Practically meaningless in fact.

If you mean what I think the premise usually implies which is that coming into existence means that matter itself came into existence, then I don't think that most of us have ever seen that happen. Everything we encounter is just a rearrangement of existing atoms.

Apparently subatomic particles do just spring in and out of existence and we don't know why and haven't found a cause. And we don't know why or how. So if that's the meaning of come into existence, then the premise fails because we've never found a cause.