Error 1120: Access of undefined properties (disabling advanced layers not an option)

[catherinet9489601]

Hello all! I have an assignment for class that went really well, except for this one issue. 

I've seen several similar posts about this particular error, but none that address how to fix it if disabling advanced layers is not an option (it disables my Camera layer, which completely breaks my parallax scrolling effect). The code for the buttons in question looks like this: 

stop();

Replay_btn.addEventListener(MouseEvent.CLICK, fl_ClickToGoToAndPlayFromFrame_7);

function fl_ClickToGoToAndPlayFromFrame_7(event:MouseEvent):void
{
gotoAndPlay("JumpHere");
}

Sprites_btn.addEventListener(MouseEvent.CLICK, fl_ClickToGoToWebPage_3);

function fl_ClickToGoToWebPage_3(event:MouseEvent):void
{
navigateToURL(new URLRequest("http://gameart2d.com/freebies.html"), "_blank");
}

Sound_btn.addEventListener(MouseEvent.CLICK, fl_ClickToGoToWebPage_4);

function fl_ClickToGoToWebPage_4(event:MouseEvent):void
{
navigateToURL(new URLRequest("http://www.bensound.com"), "_blank");
}

I've used the Code Snippets panel, and the "JumpHere" piece refers to a frame label at which point my animation starts after the button is clicked. I've double and triple checked, and the button instance names in the Properties panel and in the code are the same. 

Any suggestions are welcome, as I've already been docked 25% of my grade on the assignment based on this issue alone. I'm allowed to resubmit, so I'd really like to be able to fix it, especially since the problem is now popping up in a new project. Thank you, and I really appreciate any help!