Make sure that you have your Text symbols showing and select the end of paragraph mark as part of the entire condition. You probbly missed this for the last ListNum item, so when you set it to hide it reverted to 1.
See this thread for a similar issue: Hiding conditionalized text causes preceding list to display additional list item
I always author with the text symbols showing, so that was not the issue.
However, today I made absolutely certain that the conditional tags started at the left margin, and ended after the end of the paragraph mark after the third numbered list paragraph, and it seems to be working.
I honestly thought I had done that before, but your comment made me go back and look again.