Sorry, my fault. It looks like having quotes in the file was the problem. As mentioned, adding the quoting parameter fixes the problem.

I'd assume that if quotes are not paired, csv should raise an exception. And I don't think that all the different chunks of the file I tested, had always an even number of quotes.

Also, I don't understand why using the default delimiter worked well, and with tab delimiter the problem happened.

I'll take a look in more detail, but I'm closing this issue.

Thank you all a lot for the help!