When you have too much in your inventory you can't move. You will have to either give items to someone else or delete some things. If you equip your mercanary bandolier, you should be able to put items into it, the same as a backpack. If you were wearing a backpack and equiped the bandolier, everything that was in the backpack got put into your inventory. This might be why you are overloaded. So try moving stuff into the bandolier and see if that helps.