Why is the HLR result different than before?

There is not necessarily an issue with the HLR service. Most likely, the number has been ported in the meantime. Mobile number portability (MNP) enables mobile telephone users to retain their mobile telephone numbers when changing from one mobile network provider to another. So it is possible that an HLR Lookup shows a number belongs to one provider and an HLR Lookup at a later time show the number belongs to another provider.

Another reason is that the attributes listed here can change over time and some of them can be null because not all information is available for all countries and providers at all times. We relay the information we get live from the number when it is pinged, and this can vary due to issues with the provider or country at a certain time.