copy of an older, barely legible manuscript?

[JoJo_Jost]

I don't know. But this might work in the context of Stolfi's Reader-Author-Scribe scenario, if either the Author couldn't always perfectly represent phonetically what the Reader was saying and decided to include several variants to figure it out later. Or the scribe had to copy a draft that they couldn't read perfectly, and so decided to include several variants when the original wasn't clear.

Yes, that's what I meant—imagine that someone (or several people) copied the text from an illegible source and simply wrote down the various possible sequences, perhaps when almost nothing was legible anymore, just fragments of words—or the same words that they could still read.

My feeling is that these duplications occur in clusters.  For this reason, I suspect that the underlying manuscript was destroyed in these parts by age, moisture, and mold, because, for example, it had been left to rot in a monastery cellar for a long time.