I had already posted in another Thread saying that Graff was no longer displaying both CPU and memory used after they have been displayed for more than once. This was happening frequently and randomly after installing NS.
Day by day, the issue occurred less frequently since yesterday and the problem is gone. The last two days I have done several tests trying to reproduce the issue and I can finally confirm that the Graff preserves all the data and are regularly updated as well.
I ran a quick scan, left the computer idle so that NIS performs all tasks more than once, I turned off the computer, did a reboot and performance monitoring continues to work as it should.
From what I seemed to understand, this was due to the fact that the data were transferred from NIS to NS somehow led to having the issue.
Based on what I have experienced, I would suggest to all those who make an over the top install experiencing the same issue, to not proceed reinstalling NS, but just wait until the issue is resolved on its own.
I hope this can help if necessary.
PS: If I were to get back the same issue, I will be here to update the Thread.