UO Second Age

I understand supply and demand yet I have noticed that some vendors (in particular, Jewelry and armor vendors in Britain) will not buy goods when you say 'Vendor Sell.' If I say 'Vendor Buy,' scroll through their listing, close it then say 'Vendor Sell' then I will be able to sell them my goods. This though does not always work and this is not how it is supposed to work in any case.

Something appears wrong with it.