Each time you invoke ko.applyBindings the entire DOM is inspected for bindings. As a result you will get multiple bindings for each element if you do this more than once. If you just want to bind a new DOM element you can pass this element as a parameter to the applyBindings function:
ko.applyBindings(viewModelA, document.getElementById("newElement"));
See this related question:
Can you call ko.applyBindings to bind a partial view?