Incorrect tip amount scaling (only native currency) in partial fill scenario when using fulfillOrders

Component

API

Have you ensured that all of these are up to date?

[X] seaport-js
[X] Node (minimum v16)

What version of seaport-js are you on?

4.0.1

What function is the bug in?

fulfillOrders

Operating System

macOS (Apple Silicon)

Describe the bug

Tip amounts in native currency are incorrectly scaled when performing a partial fill resulting in a much lower fee amount being charged than intended.

The most recent SDK version(4.0.1) includes a fix intended to address the issue where tip amounts were not at all scaled to the proportion of the order being filled in a partial fill scenario when using fulfillOrders. Unfortunately that fix has introduced a new bug where tip amounts are being incorrectly scaled (scaled to a much lower value than required) because the tip amounts sent to the Seaport contract are the scaled down values when they should infact reflect the original full order view.

Scenario:

Create an order to sell 10 ERC1155 tokens at 1 ETH per token so total order value if 10 ETH.
Include a 2% fee on the order which will be 0.2 ETH for the entire order or 0.02 ETH per token.
Execute a partial fill for 2 units of the order by invoking sdk.fulfillOrders()

	Expected	Actual
Cost of tokens	2 ETH (2 * 1 ETH)	2 ETH (2 * 1 ETH)
Fees	0.04 ETH (2 * 0.02 ETH)	0.008 ETH (2 * 0.004 ETH)
Total	2.04 ETH	2.008 ETH

Note: This issue affects only partial fill scenarios using native currency which are executed by calling fulfillOrders and only seen in v4.0.1 of the SDK.

ProjectOpenSea / seaport-js