[Android] Books Downloaded Show as Not on Device

Calibre version 2.80
Calibre Companion 5.2.4.4

I have had Calibre on my desktop machine for several years. I just installed Calibre Companion on my Samsung phone. I did the following:

• Start content server in Calibre
• Connect to content server and Download All in Calibre Companion

When the phone is connected to the desktop, almost everything shows as "On Device" in Calibre, but several PDF books do not. I can see them in Calibre Companion and read them, so they are definitely on the phone. There are 333 books total, 175 are PDF format and 44 PDF format that do not show on device.

I disconnected the phone and did the same process on a Samsung Galaxy Tab A. I get the same set of books that do not show as on device. So there seems to be something about that set of books.

Has anyone seen this behavior?

Thanks!