I also appear to have the case where the same item shows up in tracking multiple time as well.

When buying an item, I always get the confirmation in chat, but it doesn't show up in tracking.

purchasing an item can take up to 60 seconds for the changes to be displayed
if it doesn't show up in tracking simply waiting up to 60 seconds and pressing sync to do a refresh should display in the sold items list. an item can only display once in tracking so you must have accidentally bought 2 different items.

If it's a limitation of the hoops you have to jump through to make this work, then there probably needs to be a tooltip\warning of some sort. I asked a similar question.

for scalability the listings pages utilize caching, this means that even though you bought out an item it can still be displayed in the listing page for up to 60 seconds (cant be bought multiple times) after 60 seconds another sync will be required to grab the fresh listing pages from the Nirn Auction House servers, when you list an item for sale it says "Successfully Listed Item(s) for sale - processing may take up to 60 seconds" I can add something like that for purchases