OSIS->Plain filter duplicates text in some rare locations in STEP Bible module NASB-TH

Dr David Instone-Brewer of Tyndale House, Cambridge has given me private access to their not yet released module NASB-TH.

I have found a number of locations where diatheke (that uses OSIS->Plain) gives a strange duplication of part of a verse.

Here's an example:

This command was used to generate the text below:
xiphos\diatheke -b NASB-TH -e RTF -k Acts 2:19-20 >Export\NASB-TH\NASB-TH.diatheke.acts2_19_20.rtf.txt

Observe the duplication error in these two verses!
The same bug occurs in a number of other places.

Acts 2:19: \u8216?And I will grant wonders in the sky above
And I will grant wonders in the sky aboveAnd signs on the earth below,
Blood, and fire, and vapor of smoke.

Acts 2:20: \u8216?The sun will be turned into darkness
The sun will be turned into darknessAnd the moon into blood,
Before the great and glorious day of the Lord shall come.

(NASB-TH)

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It still occurs with RTF output encoding, as illustrated above.
The only difference is how the quotation mark is encoded.

The actual output file is attached, as is the snippet of OSIS XML source text for the same two verses.

I am using the Sword utilities installed along with Xiphos 4.0.4 for Windows.

Diatheke command-line SWORD frontend Version 4.7

I've not seen this happen before with any other Bible module.
And I do a fair amount of regular module analysis with diatheke.