It can be fixed 2 ways.
1) Add a check for world border to the function that converts chest -> double chest. It should not lag much.
2) Add is_inside_world_border parameter and check for it to be same for both chest before converting. This parameter is set on generation and should be changed with border change (that could lag a bit if you change border significantly but you can use it for other blocks if needed)
Yes it still work in 1.8.2-pre.