Mobs and minecart stuck in block after goin thru portal

After holding wheat in hand and making the mob go through a nether portal i sent a empty minecart through the portal aswell and then continued to go through myself only to find the mob in the minecart but stuck inside the lower blocks of the portal. I have dug the mob out and replaced and relit the portal only to find wen i do the same thing again the same happens