In my textbook there is a sentence: " Ἔστι δὲ τῆς ἀπάτης ἕνεκα, ὡς φαίνεται. " My textbook tells me that here ἔστιν is a complete verb, so the accent moves forward. I just don’t know what he tries to tell me. Maybe it wants to let me notice that the predicative is not a nominative noun but a prepositional phrase?
It’s accented ἔστιν when it’s first word in the sentence (or after οὐκ). Otherwise it’s enclitic. But dogmas differ.