[Shopify] - Purchase Item event — potential bug?

I’m noticing a weird issue with the Amplitude plug-in for Shopify where no nShopify] - Purchase Item events are being fired for rShopify] - Order Created in the case where a customer used a “fixed_amount” promo code (note: “percentage” type promo codes do not have this issue). Relevant parts of the event_properties payload from the lShopify] - Order Created event that have led me to believe this is a problem with this sort of discount are shown in the image below.

To help troubleshoot, these are all the discount apps that are currently live on our store. Are there any documented cases with any of these apps interfering with the Amplitude plug-in’s ability to fire  Shopify] - Purchase Item events?

• DiscountYard
• Friendbuy
• Rewardify
• Bulk Discount Code Generator

Thanks in advance.