Latin Tax Exception in AR for Item Origin not honored in OM

We are on 12.1.3 and are using Brazlilian localizations for TAX and have defined TAX Exceptions(Brazilian Localization>Setup>Latin Tax>Exceptions>Item Origin)
by Item Origin in AR.When we click calculate tax on a SO line in OM , the exception defined is not being honored in OM  and the tax is incorrect .

However when the AR invoice is generated from this SO line it picks up the exceptions defined correctly.

Any ideas what we need to check here and fix .

thanks
rahul