What would happen if the valve between the right ventricle did not work properly

(tricuspid valve?) if so,

Oxygen-poor blood without getting oxygen from the lungs would flow backward towards the right atria, which receives oxygen poor blood from the body

Blood leaves via right ventricle without oxygen, goes to lungs, fills up with oxygen and returns to heart through the left atrium. It then moves into the left ventricle and goes to the body to deliver oxygen.