Tidying HTML - Intermittent Issue

I have a nagging problem whereby I get occasional errors where "Tidying HTML" has failed and the program returns the original HTML and my extractor patterns fail. To combat the problem I went to Options - Settings and unticked the "Tidy HTML after scraping" box and adjusted the extractor patterns to match the original HTML. The problem is that in the new configuration the program will occasionally tidy the HTML despite the box being unticked. I then have to readjust my extractor patterns once more. Is there some way to stabilize the situation?