I've twice had it happen on shopping lists where I have one item highlighted and TSM purchases a different item entirely. The first time it happened, I didn't slow down to double check everything and verify it was a TSM issue--I assumed I must have somehow clicked the wrong thing. Today, however, I double and triple checked it. TSM said I bought one thing, told me I was buying that thing (for 665g), and then bought something completely different (for 20k). This is an ugly bug. Here are the details I can give you:
Using an imported shopping list (specifically one given in a thread about flipping Pandaria level 80-85 blue items (specifically the 80-84 weapons list), though my previous incident was with a different list (the 85 weapon list). Here's what happened:
I selected the item I wanted.
I clicked "Buyout".
The dialog came up confirming my purchase. It showed the correct item at the correct price.
I clicked "buyout" again.
TSM removed the item I purchased from the list, and sorted the list by price based on the second-cheapest one of that item.
All seems good so far, except I see the yellow text at the bottom of my screen and its telling me I bought something else. So without closing TSM shopping (which currently is giving me the option to buy the second least-expensive item with "buy next") I search for the same item with auctionator. It shows that the cheap one, the one TSM has removed from the list, the one that every part of TSM is saying I bought, is still on the auction house. I buy it with auctionator. Swap back to TSM to confirm that it really is on the correct item and that it hasn't actaully bought it, then run to the mailbox to find out what I bought and how the hell much I paid for it (not good news).
So this is a pretty major bug that's hit me twice now. I assumed it must have been something you fixed a while ago cause I hadn't updated in a while, but it turns out I'm using the latest version of TSM Shopping module. Given that it's been around for like a month, I'm surprised nobody else is reporting the same issue (although I still do 90% of my shopping with auctionator). Given that, I don't know what to conclude. Perhaps my shopping list is corrupted and the issue is unique to me somehow? Either way I just thought I'd report it.
I'll be watching it for it in the future, so I won't get bit again--and while the gold I'll lose (once I sell this thing at a loss) is a lot, it's not even 1% of my current liquid so I'm not sweating it too hard.