Expected behavior

When you make changes to the Flat Rate shipping method, changes should be saved after hitting "Update"

Actual Behavior

Changes are immediately reversed.

Steps to Reproduce the Behavior

(Fresh Reaction install with Sample Data)

1. Login as Admin
2. Go to "Shipping"
3. Select "Standard Shipping"
4. Change the Rate from 2.99 to 3.99
5. The Alert shows "Shipping method rate updated"
6. Rate reverts immediate back to 2.99
7. This error appears in the console:

Error invoking Method 'updateShippingMethods': Match failed [400]