Yeah, I was confused about the "fluke" thing, too. That happened in two spots. I was thinking maybe there was something metaphorical about the tail of a whale, or that it was slang, or perhaps some bit of ancient Greek/Roman mythology or something else that I wasn't familiar with or had forgotten. But yeah, "call your bluff" is probably the right idiom.
Foreign character is in chapter 18 line 764. Anita error is chapter 19 line 8107.
There's also a "Beta ends here" line that should be deleted (chapter 19 line 5156).