Operation failed because the resulting body wouldn't be valid

I am trying to make a body of Iowa Class Battleship. I want to loft this four object at same time but some how the Shapr says “Operation failed because the resulting body wouldn’t be valid”. How could I fix this problem?

Check step by step which shape makes the loft fail.

My guess is the second from the bottom, with the sharp end point. You might need to make it more round at the end.