Two Problems: Fallback image while loading + lightbox on mobile

I have put my website into the private content tag so you can assist.

Problem 1: It appears that the fallback image on my website is showing on the desktop while the videos are loading in the video slider. I would only like to show the fall-back image on mobile or when the videos are unable to load. Otherwise, it looks sloppy.

Problem 2: I am attempting to disable lightbox on mobile. I am currently using it to show a gravity form for getting a quote. I have input the following code into the avia.js with no success. Any help would be appreciated:

//activates the prettyphoto lightbox
        var isMobile = {
    	Android: function() {
        	return navigator.userAgent.match(/Android/i);
    		},
    	BlackBerry: function() {
        	return navigator.userAgent.match(/BlackBerry/i);
    		},
    	iOS: function() {
        	return navigator.userAgent.match(/iPhone|iPad|iPod/i);
    		},
    	Opera: function() {
        	return navigator.userAgent.match(/Opera Mini/i);
    		},
    	Windows: function() {
        	return navigator.userAgent.match(/IEMobile/i);
    		},
    	any: function() {
        	return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Opera() || isMobile.Windows());
    		}
	};
	
	if(jQuery.fn.avia_activate_lightbox && !isMobile.any()){
        	$(container).avia_activate_lightbox();
        }