Looking through the weekly signal file, there seem to be a few Yahoo Finance tickers that should not be NaNs and are. An example would be this week’s signal file where DKNG US (DraftKing) does not have a yahoo finance ticker even though it is present under the ticker DKNG on yahoo finance DraftKings Inc. (DKNG) Stock Price, News, Quote & History - Yahoo Finance . I understand that not all stocks will be mapped, but I’m not sure how the mapping from DKNG US → DKNG does not go through, it might be indicative of other issues in the mapping pipeline