Sounds like they are minscans. Most likely if you look in the application event log on the server you will see several warnings from the Inventory Service stating "out of sync. full scan will be forced" or something to that effect.
If you perform a inventory scan on the affected computers they should scan in with all the data. I would recommend manually launching the invetory scanner with the /F /SYNC options.
You would also see this if you have a PXE Rep on the same subnet and the machines are doing a PXE Boot before a local boot. However, to see this over a long period of time would imply that these devices are also not sending a normal inventory scan (check the agent is installed and have a look at the local schedular tasks to see when inventory should run).
You will need to have a look at these to determine if the agent is installed properly, (or just push it out again if they are remote) the View Alert History should offer a clue as well if they are sending in scans but they are not getting inserted. If you have access to one of them do an output scan and then manually copy it to the ldscan folder on the core server... Then check the All Devices to see if its updated. If not then there will be an entry in the Alert History as to why and the scn file will be in the errorscan folder.