After much stalling and gnashing of teeth, I have begun the process of transitioning my back catalog from Aperture to Lr. After research on the process, I determined that the first step is to convert the Aperture library from managed to referenced. I have been doing it in small pieces, generally one year of images or less at a time.
The problem I have run into is that Aperture says there are 15,179 images in the 2014 folder. Thus far, using every trick I can think of, the number of files that have been relocated to managed files is 9711. I started by selecting the project (2014), and relocating the contained files. A disappointing 3360 were relocated. Then I selected each of the albums within the project, and used "select all" to select each image in each album. After all these efforts, I ended up with 9711 relocated files.
Looking though individual images in the Aperture library, they all seem to have the badge indicating that they are referenced files. I haven't found thousands images that have not been referenced.
I am terrified that I will lose images in this process. I have more years of images yet to go through this process. Any guidance would be appreciated.