On my turn this happened:
I had “Maw and Paw” on board from the previous turn and got a correct cost reduction of 5 mana to the Stitched Giant in my hand. I still had 5 corpses to spend so I played Corpsicle to reduce the cost of Stitched Giant further - but the corpses spent by Corpsicle didn’t reduce the cost of Stitched Giant.
In many other games Corpsicle reduced correctly the cost of Stitched Giant. It’ seems that the double cost reduction - first from “Paw and Maw” and then in the same turn from Corpsicle bugged out so that only the reduction from “Paw and Maw” was applied.