BillboardCollection problem.

I am trying to add some billboards to a collection but I encountered a strange behaviour.

If I add my billboards directly to the cesium primitive collection they gets rendered:

If I use a BillboardCollection the billboards will not show.

I create the billboard collection this way:

billboards = new Cesium.BillboardCollection();

then I add the billboards:

If I do the same with a primitive collection it works.
What am I doing wrong?

Were you able to figure this out or are you still having trouble?

Unfortunately no; in the end I used an array of billboard to handle the collection because I could not find the issue. The code worked fine in a "clean" project so the error was somewhere else.

very odd, let me know if you run into it again.