Importing from a catalog only some images copied over

I'm trying to import a set of images from a catalog on my laptop to a master catalog on my desktop. The laptop LR folder hierarchy copies over mostly correctly (at least one folder is not recreated in the destination LR catalog). Many LR destination folders are populated correctly with the source images. However, many LR destination folders contain only a subset of the source images. What images are copied or not copied into the destination catalog appears completely random. The missing image Previews are captured in the "Failed to Copy" Catalog on the desktop catalog. Inspecting the destination folders with Finder shows that the missing images are physically absent and not an artifact of LR misreporting.

Does anyone have any ideas or suggestions as to how I solve this problem.

I am using LR 6.7 on both the laptop and the desktop and both are Macs. The photo images, previews and catalog are all in the same top-level folder on the laptop.