I've stumbled upon an issue that seems to exist only in P3Dv4. I don't think I've encountered it in other sims.
Any autogen I create which has but a single default autogen object in that cell (specifically the ag_telephone object pole; found in Scenery\Global\scenery\autogen.bgl; GUID: 46f3d6cb-4270-4373-aee9-89fb38462ea9; default.xml reference: 960b0c53-4824-d848-e7ea-3e9475d18c29) causes all trees in that cell to disappear. Buildings and other autogen objects remain unaffected.
Above you can clearly see the one cell on my island of Barbados which does not contain a telepole.
This is the same autogen object since FSX. It has remained unchanged. But as far as I can recall, this does not occur in previous sims. Has anybody encountered this and found a potential solution?
The only fix I have for now is to remove all telepoles from my scenery autogen, which is a shame.
I could just create my own telepole object and add it to my custom autogen (which would probably also save some polygons) but that's low priority and I'd still like to figure out why this is happening.