When trying to answer a previous question about the patronymic derived from Asclepius, I came across the following quotation from Beekes in the Wikipedia entry on Asclepius:
The name is typical for Pre-Greek words; apart from minor variations (β for π, αλ(α) for λα) we find α/αι (a well known variation; Fur. 335–339) followed by -γλαπ- or -σκλαπ-/-σχλαπ/β-, i.e. a voiced velar (without -σ-) or a voiceless velar (or an aspirated one: we know that there was no distinction between the three in the substr. language) with a -σ-.
I'd like to know more about the α/αι variation. Which words is it seen in? It is only seen in certain phonological contexts? I'm also interested in knowing whether this alternation implies anything about the length of the vowel in the variant with the monophthong α. I guessed in my answer to the linked post that Ἀσκληπιός would have a short vowel, but recently I came across the Latin word crāpula, which has a long vowel and seems to be derived from a variant form of Greek κραιπάλη, which has αι.