I noticed in v1.988 the plot sometimes isn't generated (no <plot> in the xml) when there isn't a plot to be found on imdb (which could be correct), but when you browse through movies after that, you will see the plot from another movie in the plot field.
When you re-scrape the movie, it will always put a empty plot in the xml.
Maybe it is better to empty this field before filling it. So you could avoid wrong information if a field isn't in the xml file. At this moment, it's like some fields are emptied before reading the xml, others aren't.