Factual error: Oswald says that "Vermeer only painted twenty-six paintings and three of those are dubious." There are in fact thirty-five known to be extant (one recently stolen) of which only one is regarded as dubious. In addition, there have been descriptions of six (or possibly eight) others that seem to be missing.
Factual error: Alba Bewick tells Oliver that she wanted to have twenty-six children. Her first child, Alpha, did not survive; her second was her daughter Beta. Oliver tells her there aren't twenty-six letters in the Greek alphabet, there are only twenty-three. There are in fact twenty-four. [This is quite possibly the character's mistake rather than the author/director's. There is a scene later in which Oliver and Oswald playfully and deliberately give Beta bits of obviously wrong information (00:39:27). Besides, director Peter Greenaway delights in playing games with his audience - to put it mildly. Also, at one point Oswald mentions that Vermeer painted twenty-six paintings, of which three are dubious (00:35:13-15). This gives us the same totals as Oliver's two alphabets. Was a connection intended (whatever the point might be)? At another point (00:53:12), Oswald catches Oliver in an egregious error, establishing his fallibility.]