TD Ameritrade "Purchase Price" not matching fulfilled order purchase price

Under the positions portion of the TD Ameritrade website, my purchase price is being listed as "56.xx" while under the history of the order, it shows the purchase price as "49.xx" which is in line with the limit order I placed to purchase at "50". Yesterday, these boxes in positions were exactly what I expected. What is going on? I would expect the purchase price to not be able to suddenly change — I purchased it at "49.xx"! Is this some sort of bug with the site or have I missed something?