I have an issue that Netsuite Support cannot seem to solve. Sometimes, an item fulfillment is created and it drops the shipping cost to $0. It's infuriating to track because changes to shipping cost do not show up in System Information, so there is no way to see why this is changing or being set at $0. Does anyone have any ideas what it could be? NS support has been "researching" and looking into this for months now without any ideas.

I would recommend taking a hard look at any customizations you have on the item fulfillment. User Event Scripts, Client Scripts, Workflows. Also might help to confirm that the problematic transactions have the same shipping method and other related fields to rule out a config problem.

I'd make sure your shipping addresses are complete if you are using an integrated ship method

Thanks guys, I'm trying to look into all of these things very closely. Addresses and shipping method / shipping fields have been normal. We have shipping costs entered statically, so no calculation. It's just hard to reproduce, because it only happens 2-3 times a month (out of thousands of transactions).