Inventory asset is a summing account, in fact all parent account are summing accounts and should not be posted to.
Inventory asset tracks the item by name, and keeps qty and cost per name.
Having a sub account (inventory asset:puzzles) just confuses things within QB.
When you get a vendor credit QB is not set up to allow for a reduction in item cost, partly because QBO keeps FIFO inventory but also because it was never programmed to allow for it. So vendor credits or refunds are booked separately.