Well, this is the sort of glitch that causes many of us to be reluctant to import gedcoms -- and why we suggest starting with a small gedcom.
Apparently the software that created your gedcom stores "Sources" separately from the "Citations" that it attaches to facts. Depending on how a particular citation or source was stored, it may or may not get included in the gedcom. If you can dissect the original record for one of these profiles and compare it with what got imported here, you might be able to find a pattern.