Thank you for the advice. I went through the whole database, checked all the customers, changed a few to 'trick' the system and still quite a few customers are missing. Also turned on the verify report group option. I changed the ones who are missing several times, type in the report group as well as chose it with the finder. I don't see anything different with those customers. They are all active as well.
We will do a DIC today or tomorrow to see if errors show up.