到达页面底部时，粘性导航栏会闪烁

I recently go my nav bar to act as a sticky nav bar that adheres to the top of my page after I scroll down to a certain point, however, when I reach the bottom of my page the entire nav bar flickers, and even disappears sometimes. Think of it as an old TV that would flicker and you would end up hitting on the side to stop the flickering. How would I hit my nav bar to stop it from flickering. I recently go my nav bar to act as a sticky nav