This problem would go away if the three nations ' markets could all be searched from one location. Then it wouldn't matter where you sent your retainer, everybody gets to sell their stuff, people suddenly forget there was a problem in the first place, bam. problem solved.

Even if the whole retainer thing disappeared and the whole system was changed, they'd still need to make sure there is just one global trade system instead of splitting it into three, making this the supreme thing that needs to be changed over any other aspect of trading.