I had a problem this week with a client where a specific information was not replicated to the primary after a hardware inventory.
After the new policy was distributed and the hardware inventory scan finished on the client, the data start to replicate in SQL database.
I recently had a problem with client inventory data not being present in the SCCM database.
Somehow my management point had stopped inserting data into the tables.
I resolved this issue simply by removing and re-installing my management point role on my SCCM server, but it lead to several hours of head-scratching!
I was making a query to find machines running Windows XP with Service Pack 3, and it only reported back 4 or 5 clients, even though I knew that a lot more had the service pack installed.
I checked the logs on some of my clients and they seemed to report both hardware and software inventory just fine, and sent it to my management point.