I have recently bought the unlimited PHP Sitemap generator. My website contains about 11k pages. When I execute the sitemap generator, it stops every few minutes(generally about 70-100 mins). I am running the generator in Background. In the Crawler limitation configuration section, I have put everything as unlimited. In my command line php.ini file, I have max_execution_time = 0 and memory_limit = -1. I have 4Gb of free memory in my machine. What's going wrong here?