A recurring product is not calculated correctly in the cart

[f1-outsourcing]

At first I thought coupons are not working on recurring products. But from the screen capture you can see a green confirmation message that the coupon was applied. So maybe we can just assume that coupons are indeed implemented for recurring products. However when you compare the cart with a 'normal' product. You notice that totals are not correct.
So maybe this problem is not with coupons, but with the calculating totals of recurring products. If totals are 0 how can the discount be applied? I have seen these incorrect 0 totals before.
Maybe somewhere something is missing where prices are 'extracted' from recurring products correctly?

Preconditions (*)

v20.5.0

Steps to reproduce (*)

*product price before coupon was displayed as 12 in totals. Looks like something is subtracted.

Expected result (*)

This is how a not recurring product is in the cart

updates that could narrow down where the issue is

• When completing the order without coupon. In the admin the €12 is back, and the VAT seems to be calculated correctly. (so maybe only display issue, notice VAT not having exchange rate applied)
  

• When completing the order with coupon, coupon is not marked as being used.

• When completing the order with coupon. The correct discount amount is applied. The correct VAT is calculated over the discounted item. However Subtotal, GrandTotal, TotalDue are incorrect. (From this screen capture it also looks like the VAT has no exchange rate calculated)
  

[ADDISON74]

This part of Magento related to recurring products has not really been analyzed over time. Since I have been here I have not seen any reports. I appreciate that you have the time and patience to find the problems. I hope we can find solutions so that no one is affected by the malfunctions of the code.

[f1-outsourcing]

This part of Magento related to recurring products has not really been analyzed over time. Since I have been here I have not seen any reports. I appreciate that you have the time and patience to find the problems. I hope we can find solutions so that no one is affected by the malfunctions of the code.

My intentions are not that honourable ;) I am just looking to start a new business that heavily leans on subscription services.

[f1-outsourcing]

This is something I would consider sponsoring ;). I tried a little with xdebug trace files but don't really know what to search for. Probably much easier for someone experienced who understands how quotes / totals work.

I was thinking of using partial credit memo's as a work around, but then I first need to create an invoice and when I created an invoice the order is not being searched for when assigning payments because it is considered paid / 0 due.