Crafty_error.txt is a log with all the error that are detected by the script, it helps us a lot in searching for errors made in Crafty or anything that could effect the script ( that later on we find a way around it to fix the issue ). It is not on all the time because Crafty will always detect one error. " cannot apply file outpu_log.txt " It will never be able to apply it as it is deleted after the patch is downloaded. It is important for us to keep our users project clean and tidy. That's why all not needed files are always deleted instantly after patching is finished. Because we don't want to annoy anyone we usually keep this option on false and only change it to true when it is needed in search for an error.