So on the market if someone accepts a trade you post on the market, all related trades on the market are still there.
so for example
War axe for bec
War axe for long bow
War axe for stick
is on the market
if someone accepts the war axe for stick then the bec and longbow trades remain.
Solution to this would be to check both parties if they have multiple copies item when the make the trade rather than just the person accepting the trade.