In the template eCom/Order/OrderLines.cshtml the template tag used for the discount price is Ecom:Product.Discount.Price.PriceFormatted but in other templates like eCom7/CartV2/Step/Helpers/OrderLineItem.cshtml the template tag used is Ecom:Order:OrderLine.UnitPriceWithProductDiscount.PriceFormatted
This causes some inconsistencies like in the order email having a discount price larger than the unit price, when in the order confirmation there is no discount present.
I was able to fix this by replacing Ecom:Product.Discount.Price.PriceFormatted with Ecom:Order:OrderLine.UnitPriceWithProductDiscount.PriceFormatted in eCom/Order/OrderLines.cshtml
DW Version 9.15.9