NS not always completing Full System Scan

I need some help with Full System Scan. It’s scheduled to scan at 12:00 pm on Fridays, Prevent Standby, Only on AC. It’s been scheduled like this forever. It used to scan 2,000,000+ which, I assume, includes the USB hard drive I use for backups. Then it seems around the end of April it started hit and miss scanning 700,000+ taking an hour or so, off and on with 2,000,000+ which takes 2+ hours. Now, since the beginning of July, it is only scanning 700,000+. Even if I do a manual full system scan.

Friday:

6/30  2,971,827 Total Items Scanned

7/7      793,996

7/14    767,418

7/21    771,873

7/23    769,098

8/4  3,057,234

8/6  3,068,465

8/11   773,243

Why is it doing this? I use the computer some during this time which never seemed to effect it before, if that’s what the problem is. I don’t have any other program scanning. Any suggestions please. Thanks.

Windows 7 IE11, NS 22.10.0.85