I've been experiencing an issue with one of my MemberGroup discounts for Free Delivery. I've already posted this issue on uWebshop's GitHub but am reposting here to try and catch the wider Umbraco audience.

When I get to the checkout stage, every single person gets the Free Delivery discount, despite the fact that I have restricted it to only a single MemberGroup. Even unregistered (i.e. not logged in) users get the Free Delivery.

When I look at the order in the database, I can see that it has the discount applied:

<Discounts>
    <OrderDiscount>
        <OriginalId>22484</OriginalId>
        <DiscountType>FreeShipping</DiscountType>
        <DiscountValue>0</DiscountValue>
        <RangesString />
        <Condition>None</Condition>
        <NumberOfItemsCondition>0</NumberOfItemsCondition>
        <RequiredItemIds />
        <MinimalOrderAmount>0</MinimalOrderAmount>
        <IncludeShippingInOrderDiscountableAmount>false</IncludeShippingInOrderDiscountableAmount>
        <MemberGroups>
            <string>Discount Member Group</string>
        </MemberGroups>
        <AffectedOrderlines />
        <Tags />
        <OncePerCustomer>false</OncePerCustomer>
        <Id>22484</Id>
        <TypeAlias>uwbsDiscountOrderMembergroup</TypeAlias>
    </OrderDiscount>
</Discounts>

Now, I've tried clearing my browser cache and cookies, using incognito mode, different browsers, different computers, and every time this happens. I've also cleared out the Umbraco TEMP folder and restarted IIS.

I'm beginning to suspect that something has become "stuck" in Umbraco somewhere but I'm not sure where to look or how to diagnose this issue. Anybody out there experienced this or have an idea where to start?

Any assistance greatly appreciated.