If you put in the order to sell at the market - you'll get a buyer eventually but there's no guarantee you'll like the spread or the fill.
What happens during 'fast' market conditions is that the buyers just disappear for a while - and then the ask drops and drops until the buyers think it's fallen far enough, and suddenly all the sell orders get filled down at the new price.
In a liquid market this all happens in seconds, but I guess in the Rough Rice pit or the New Zealand lambswool market, it might take longer for a buyer to act.
Or they might put in a really really low bid.
Or assuming that there is a book of limit orders waiting to be filled, if you put in a market order it will move the market down to the next Buy Limit. I don't know what would happen if there were no orders in the book. I guess you'd just have to wait.