dpg

I know it sounds crazy, but I wrote down my registration key in a book. Don't want to sound like a smartarse, but it works.

I had the same problem on my Windows 10 computer. Fortunately I still have a Vista computer up and running, so it was easy to transfer the files and just install them like any other item of scenery. This worked fine for me.

I am certainly no expert, and what I have to contribute may not help at all. However, I make objects mostly for my own use, and I believe that the 'pop-up' distance is related to the size of the object, and that may be why the objects you describe having an issue with are very small objects. For my own objects, I add a single, untextured,inverted triangular polygon below ground level, and I seem to be able to control the pop-up distance according to the size of the object and the size of the polygon. This is entirely my own experience, and I would be happy to hear from anybody who has more knowledge.