Procedural Foliage Spawner only spawning one element

Just wondering if anyone who has encountered this, worked out what what wrong? My files in a colleagues computer, or ones created from scratch is only spawning on foliage type, which has been correctly set up, and referenced in the spawner being used by the volume are only spawning one layer. We can change that layer to anything and it works, but we can’t have more than one working element in the spawner.

We’ve tried creating Foliage Type files and Spawner files from scratch and tried using ones from other working projects (making sure all references were correct)
We changed seed values, collision values, shade values, any parameter that could be changed was, and still only one of the array elements spawned.

Any ideas?