I think the issue was that words in the 'word-of-the-day' list are not repeated in the dictionary, so removing them from the 'word-of-the-day' list meant they w

I think the issue was that words in the 'word-of-the-day' list are not repeated in the dictionary, so removing them from the 'word-of-the-day' list meant they were also no longer valid guesses. Presumably this was pointed out to the NYT, and at some point they fixed the bug by adding any words removed from the 'word-of-the-day' list back into the valid guesses dictionary.