Prepositional phrases are generally adverbial, but certainly not always. Sometimes it can be difficult to tell what they modify.
Take Acts 14:1 for example. Paul and Barnabas have just been run out of Pisidian Antioch and have entered Iconium. The NIV reads, “At Iconium Paul and Barnabas went as usual (κατὰ τὸ αὐτὸ) into the Jewish synagogue. There they spoke so effectively that a great number of Jews and Greeks believed.”
The Greek is, ἐγένετο δὲ ἐν Ἰκονίῳ κατὰ τὸ αὐτὸ εἰσελθεῖν ⸀αὐτοὺς εἰς τὴν συναγωγὴν τῶν Ἰουδαίων. So what does κατὰ τὸ αὐτὸ modify?
I thought the NIV was pretty straightforward. “According to the same” is adverbial, the point being that it was their custom to first go to the synagogue when they came to a new town.
The NASB has, “They entered the synagogue of the Jews together” (also ESV; KJV has “both together”). BDAG B5bα gives “together” as a possible meaning, citing 1 Sam 121:11, so presumably they have some evidence of the meaning of the idiom. To me this sounds redundant and therefore less likely. Of course they went in together; Luke just said that a few words earlier.
The CSB is unfortunate. “In Iconium they entered the Jewish synagogue, as usual.” It sounds to me that it is saying Paul had a normal way of entering the building, perhaps through a back door? I know that’s not the case, but by placing “as usual” next to “synagogue” the prepositional phrase sounds adjectival to me.
The NET reading is especially odd. “The same thing happened in Iconium” (also NLT). They are connecting κατὰ τὸ αὐτὸ with the preceding Ἐγένετο δὲ ἐν Ἰκονίῳ.
Idioms can be especially difficult to translate, and Acts 14:1 is a good test case for the flexibility of prepositional phrases.
I haven’t beat this drum in a while, but so much for the myth of a literal translation, or the myth of the English translation reflecting the underlying Greek structure. Translating word for word would be nonsense, and there is no way an English reader could get from “as usual” or “together” back to a prepositional phrase.