I see it show discount in Magento 2 admin order details page . But I am unable to find out the reason of discount . There is no catalog price rule applied. Can anyone give me idea how i can find out that ?
I had the same issue and I had deleted cart rules after applied on order. I have tried another order with same cart items and it is working fine to me.
Please clear all the cache after disabling or clearing cart rule.
It seems cart item rules apply here without coupon code.You can confirm it by checking all cart rule from
Admin->Marketing->cart price rules.
Check all cart rules and sure you have not any rules.
Since it cut half price hence may be any rules applied before and it is deleted now.
You can reorder same product by disabling all cart price rules for some time and that will confirm you.
Hope it will help you.