Colorbox failed to load when aggregation is enabled.

Okay I solved this issue. It had probably nothing to do with colorbox at all but I am not sure. It looks like links to colorbox were rendered with subdomain instead of main domain. So basicly I had all the thumbnail images loaded properly with links like https://domain.tld and links were rendered with https://sub.domain.tld instead of only pointing to main domain.

I am still not sure what triggered that, it looks like it has something to do with how the server is set up.

Since I had no time digging into the server stuff and this was the only field having the problem I solved it in theme JS file with the following code:

$('a[href^="https://sub."]').each(function(){ 
	var oldUrl = $(this).attr("href"); // Get current url
	console.log(oldUrl);
	var newUrl = oldUrl.replace("https://sub.", "https://"); // Create new url
	$(this).attr("href", newUrl); // Set herf value
});

I am just leaving the code here although it is highly unlikely someone will have the same problem.