I have just found the issue and I still don't really understand it. Not that it matters

I had Universe 1 set to 35 channels in size because I was going to drive some flood lights that didn't pan out. It was an odd number because the floods started on channel 2. At that stage the trees were 21-35. When I gave up on the floods I changed the trees to be 1-15.
I had an idea (it was idea number 43567) that I should just allocate all the channels available on the AVD48. On the setup I changed universe 1 to be 48 channels then went and updated all the models after the trees by adding 13 to their starting channels......and it worked.