Your code looks okay, can you post a more complete example that causes the problem? We haven’t seen anything else like this before. I assume there are no errors in the console?
Hello, in javascript, I had same issue with array of objects.I changed my code in order that each element of array has the requested information. For example a workaround will be to make a loop on the billboardCollection because in each of your billboard, you designed an id attribute equals to "track.uid". In this case "map" array isn't a mandatory.