What are the problems of medieval trade?

The main problem was the speed of cargo delivery. The fastest transport was by sea at that time, but the level of shipping had not yet reached such a high level that ships could move by sea, far from the coast.
Land caravans did not travel long distances; there were many resellers in the cities. Why the price of goods increased greatly.
The trade links themselves between the cities were weak. And therefore, it was difficult to negotiate directly between manufacturers on deliveries.
It was also required to constantly carry money with you, which attracted the attention of robbers, of whom there were many everywhere.