There is something screwey about scripting in Photoshop CS

I have a script that aligns some text layers in a PSD.

It works great in all my test cases.

I then get a customer PSD and it doesn't work, it messes everything up.

Debugging claims that Photoshop thinks it is doing exactly what I tell it.

Deleting the layers and re-creating them exactly as they were fixes the problem.

It would be nice if my new knowledge today was the underlying cause of this behaviour, but alas it is not.

All I have discovered today is that Photoshop is inconsistent and that I am not as clever as I think I am.