I am wondering if this is a sim bug or just something I am doing wrong - so first up, a picture.

In the image the trees on the left have been manually placed, and are behaving as expected - the LOD is changing at 75m out to a simple quad tree. The trees on the right however are placed within an 'Asset Block' for placing the bulk assets - as you can see these trees fail to change LOD at the same time as the manully placed versions and then simply vanish when you move slightly further away (probably because the camera is no longer within the LOD range).
What is interesting is if I click 'Edit Placement' in the block asset flyout the LOD model displays correctly.
As these trees are for a route project that is around 90% forest fixing the Asset Block problem is a must - if it is at all possible.
Thanks in advance for any advise you may have :)