Inventory module in 2007 is defective

We implemented on 30th April 2007, so N/S debugged their inventory module on us, but in spite of that I am still getting this inconsistent and disconcerting inventory activity :

Inventory Item   
10000-07538    115
Invoice 01/06/2007 13G0134807 Cost of Sales -60
Item Fulfillment 01/06/2007 GPL0124607 Cost of Sales -60
Item Receipt 05/06/2007 GRN0269007 Cost of Sales Adjustment 0
Item Receipt 05/06/2007 GRN0269007  60
Item Fulfillment 05/06/2007 GPL0125507 Cost of Sales -10
Item Fulfillment 07/06/2007 GPL0126307 Cost of Sales -30
Invoice 07/06/2007 13G0136707 Cost of Sales -30
   
Total - 10000-07538    -15
   
Total - Inventory Item    -15
   
Total    -15


Does anyone out there know how to fix this problem - Netsuite dont.
Maybe the code is defective.