So here is where I am stuck and need some help or guidance.
 
I created a report to assign the contacts with various hobbies to the 4 Hobby Types using a bucket field
 
The four hobby types (Outdoor Activities, Arts and Crafts, Extreme Sports, and Other) are listed in the left column of the report as groups, followed below by the Account Name, Contact Full Name, and the actual Hobby name for each hobby type.
 
Everything works as expected EXCEPT 16 records that show up as if they had no hobbies at all. Yet they do. Some have two hobbies, others three but they never get assigned to one of the 4 buckets. And the hobby name never shows on the report. And contacts with two or three hobbies should show up in the report the same number of times as the number of hobbies. But each contact only appears once. It is as if the software is just not seeing these Contact Hobbies for these specific 16 records.

Even though those hobbies are part of the bucket assignments.(In other words, other Contact records with Kayaking as a hobby get assigned to Outdoor Activities just fine but Kayaking appears as one of the hobbies in these 16 records) but never appears in the report. Every record has a Contact ID and an Account ID. In other words, the relationships between Accounts and Contacts is present and working nominally

The Hobbies were imported and there appears to be no difference between these 16 records and the others that work perfectly.
 
The Hobby Type is just "-" on the report. A hyphen, nothing else. Can't filter to get rid of these 16 records either.
 
Of course, this makes it impossible to do the Lightning Contact Hobby report where I filter for only records with the Outdoor Activities type.
 
The "-" type is always there every time I run the report. (Never there in the preview)
 
I added a filter to exclude records without any hobby and that works fine. Those are the records I would expect to see in a <NULL> bucket had I not filtered them out of the final report.
 
So the assignment to create a report on contacts without hobbies completed without a problem.
 
What might be causing these 16 records, all with Contact Hobbies, to not get assigned in the bucket filter that works on all the rest of the records just fine?

Data Corruption?

I exported all the records in the Contact Object and all the fields. The 16 records look just like the rest that work properly.

I was thinking of using the 16 records to make a list of Contact ID's to delete, then re-import these 16 records that just won't behave normally.
 
Steps to fix? Ideas?

Please, can anyone help me solve this? If screenshots would help, let me know and I will provide them.