it might have something to do with how your kindle formats notes in your clippings. When I make a note on my kindle, it looks like this in My Clippings.txt:
Instapaper: Wednesday, Dec. 2nd (Instapaper)
- Your Note on Location 505 | Added on Thursday, December 3, 2020 7:16:57 PM
Check how notes are formatted in your clippings file, because what should be happening is that the program looks for the word “Location” then takes the first number that occurs after it (in the above case it would be 505). If the word “Location” isn’t there, then you’d probably get a bug