At 1:36:42 Rembrandt says that Geertje doesn't wash herself. Just 1 minute later he says he saw her undressing to wash.
At 1:06:37 Rembrandt says Marita threw herself of the roof of the Westerkerk. Earlier in the movie Marieke said that it was Marieke's mother who jumped of the Westerkerk.
The militiamen said it annoyed them that Rembrandt was going to look at them forever through his small self portrait in the painting and that nothing could be done about that. They could have erased it, though, by over-painting. That was no exception in those days. Since they haven't done that, the plot is not probable.