1)Delete the book on the kindle.
2)Also check (with the kindle as USB drive on the PC) in the documents folder if there is another copy of the book that might not show up on the kindle (this can happen in case you transferred the book at any stage without having set the ASIN after re-packing with kindlegen).
3)Then transfer the book again with calibre.
If this doesn't help you could try deleting all collections or even the cc.db but that would be a bit drastic if the only problem is one book showing as PDOC.
P.S. The easiest way to set the metadata correctly is to include a mobi-asin:BXXX (where BXXX is the Amazon asin) tag in the Metadata editor IDs: field in calibre (can also be asin: or Amazon: instead of mobi-asin) and then use the Quality Check Plugin -> Fix ->Fix ASIN for kindle fire.
https://www.mobileread.com/forums/sho...d.php?t=125428
For my use, I have changed the mobi6.py in the Quality Check.zip file by commenting out the line that changes exth504 because this is not necessary for the Kindle Touch:
if asin is not None:
update_exth_record((113, asin.encode(self.codec, 'replace')))
#update_exth_record((504, asin.encode(self.codec, 'replace')))
if cdetype is not None:
update_exth_record((501, cdetype))