Actually, I just caught that, and made the change.
Same results.
If I de-select Douban in the metadata source list of preferences, it finds the book perfectly (listing all three of the sources, with the correct info and everything).
Unfortunately, if I go back and turn Douban back on, and re-search for the book, it doesn't find the right one anymore.
It seems that Calibre is, for some reason, letting the result from Doubon over-ride results from other sources (even if there are three alternate sources that agree with one-another)...