Here is the thing if the 2nd squad had cut their own rope wouldn't it be better that the 3rd attempt is made by having a rope that can't be untied by the person attached and uncuttable? That way you can force the person to return? But I guess the author has planned for that door to be an instant...
I am more surprised that they added a Vietnamese character last time i remember was Sun Ken Rock was the last time i read of a manga that had a character from Vietnam