I made a similar post on Reddit, but I’ve placed additional details here.
Greetings,
I have been using a spreadsheet to keep track of my Ancient Greek language deck. Recently, I started having a problem with duplicates. I deleted the whole deck I was working on and reimported; now EVERY card is duplicated.
The *.csv file was renamed to *.txt and has the following headers:
#separator:Comma
#html:true
#deck column:1
#tags column:2
The basic import options
I have also used the default Notetype (Basic) as well as Preserve and no option fixes this issue.
There is this KB article that says to simply delete the note, but this is not practical for ~5000 vocabulary cards and grows every time I re-import with new vocabulary.
I am a programmer so I was importing using the Anki Connect plugin, which I have removed, and tried to re-import but still to no avail.
I suspect that the issue is due to card detection and merging, with regards to UTF8 accent marks in the Anki eco-system. Google Sheets has an issue with searching for Greek accents even if I copy the word, so perhaps Anki has similar problems? This doesn’t explain why it was working fine until recently.