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In going through the Gospel According to John, chapter 9, I notice the evangelist uses three different aorist active indicative forms of ἀνοίγω:

ἀνέῳξεν (double augment) in 9:14
ἠνέῳξεν (triple augment) in 9:17
ἤνοιξεν (single augment) in 9:21.

It's not like Homer, where variations in declension and orthography abound in order to fit the meter. John's gospel is unmetered. What's going on here? Why would an author use three different forms of the aorist active indicative?

This might indicate that the evangelist is combining material from three independent sources? Anybody ever read anything in the various commentaries about this?

Smyth notes in his list of verbs that impf. ἤνοιγον and aor. ἤνοιξα forms
in Xenophon are probably wrong. The imperfect and aorist in Attic should be ἀν-έῳγον and ἀν-έῳξα respectively.

In late Greek, according to LSJ, we find very irregular forms as the ones you wrote.
It's possible that the writers of this gospel jumbled up their Greek or perhaps the fault is with
the manuscripts' editors/copiers.