Item description on an order not the same as the description in IC Items.
The item description on an order is being pulled from item pricing, not from items. When you update the description in Items, it does not automatically update the description in Item Pricing. You will need to update description on item pricing as well, in order for the new description to show up correctly on orders. Once the description is updated in item pricing, delete the line from order and then re-add it to show the correct description. The change will not be reflected on any already posted documents.
If you have many item descriptions to update, using an import may be the fastest way to get them all into Sage.