I don't really get what's going on because I missed the screenshot in the OP, but I do remember my sister saying she went to collect some items because someone had a buying shop up in which he offered a very gratuitous price for them. When she returned with a good number of the items, she couldn't sell them to him due to an error she didn't really understand.
I figure if you then open a shop next to that person, selling the items he's buying for a price slightly lower than the price he's buying them at, people will eagerly buy them off you to make a little profit by reselling, right? In theory, you could do this with an absurdly huge number of items and make tons of money because the bugged buying shop won't disappear until he actually receives the items he's buying. Is this bannable? As in, is it considered a glitch exploit?