In some models transports costs may alter the equilibrium, but if we believe that Efficient-market hypothesis holds, then we must expect that prices fully reflect all available information then no suboptimal equilibrium is going to be implemented.
However, in the Walrasian tâtonnement could be affected by transports costs increasing the prices and therefore, reducing the traded goods. We can even argue that if we introduce highly enough transports cost then goods become non-tradable.
But even in presence of non-tradable we can find a Walrasian equilibrium where every agent consumes his entire endowment.
So, what type of distortions do you expect to happen when transports costs are introduced in the Walrasion model?