Check the equip you put into the weapon slots. You cannot use more than 4 slots. That means 1handed swords -> 1 slot, shields usually -> 1slot (except for Huscarl Shield), 2handed -> 2 slots, polearm -> usually 2handed, bows -> usually 1 slot (except for Long/Rus Bow -> 2 slots), arrows/bolts/throwing weapons -> 1 slot
That means you can take a 1handed sword, a 2handed sword and a shield with you for example: 1+2+1=4
You cannot take 2 2handed swords with you plus a shield: 2+2+1=5