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Hello, medium time user here (4 years).

I finally decided to join the community. I've been able to help dozens of people at my university and thought I might be able to a help out a bit here as well as get an answer to problem of mine.

I'm have a similar problem with natbib and the chicago style. I get this output warning
Package natbib Warning: Multiple citation on page 1: same authors and
year without distinguishing extra letter, appears
as question mark.

This is the concerned MWE.
\documentclass[letterpaper,11pt]{article ...