The extended choice plugin will fail when used with remote builds. The parameter will not be recognised as being passed.
In the plugin the following function is incorrect:

public ParameterValue createValue(StaplerRequest request) {

String value[] = request.getParameterValues(getName());

if (value == null)

return null;
}

Note here that if the parameter is not set, it will set a default value. Otherwise it will always return NULL when it should return the current value, as something like a new ExtendedChoiceParameterValue.