Hello gentelmens

So im truing to make some ribs on a bit complicated shape.
In the start the ribs was just a planes with "Shell" applyed.
After i trim those ribs by main body and make boolean union.
The first two ribs - doesnt make any trouble. Im even able to make a fillet.
But second two doesnt union, instead of this they just leave partially cut on main body.

How this can be solved?