The Everything Store is shrinking again. Amazon customers who want to order forthcoming Warner Home Video features, including “The Lego Movie,” “300: Rise of an Empire,” “Winter’s Tale” and “Transcendence,” are finding it impossible to do so. The retailer’s refusal to sell the movies is part of its effort to gain leverage in yet another major confrontation with a supplier to become public in recent weeks. In a standoff with the Hachette Book Group, Amazon is refusing to take advance orders and delaying shipments. Amazon and Hachette are wrangling over e-book terms. The retailer is in a third standoff in Germany, with the Bonnier Media Group. Disputes between retailers and vendors happen every day. What is unusual here is not Amazon’s relentless desire to gain margin from its suppliers, but the suppliers’ growing resolve to hold the line.