I actually just spent a really long time figuring out answers to this question by piecing it together from the spotty documentation and a lot of web console inspection. Sinc
I was having problems that calling the below code in the $('NextButton').onclick method was forcing $('NextButton').onclick method to be called twice. Removing it worked for me so the onclick method gets called only once but still moves the survey forward.
// and now run the event that the normal next button is supposed to do
Qualtrics.SurveyEngine.navClick(event, 'NextButton')