Value Filter Greater than Not Working

Hi,
I am trying to filter values from 10/1/2016 - 12/31/2017 to show sum of only greater than zero values but it's not working properly. In the attached picture you would see that Sep 2017 there's a negative value shown for warehouse location Davenport.
Also, I am still want to show all the months blanks between 10/1/2016 - 12/31/2017 if they had only negative values. As you can see Feb, Apr 2017 are skipped and Oct-Nov-Dec are not even there. Bear in the mind that there's no value yet for Oct-Nov-Dec but i still want to show those months blank in the table.
See attached

Hard to work with a picture

I understand but there's too much sensitive info in the data source

To give you an idea here are the filters that are currently applied in this pivot table
Column Label Grouping from 10/1/2016 - 12/31/2017 (left the boxes unchecked in grouping dialog box) By "Months" and 'Years"
Value Filter of Column Label "is greater than" zero