Same issue i had a few weeks back and still no solution.
On three laptops i have an issue with live update or quick scan using 100% CPU and failing to end the process.
On live update it finds the update, downloads the updates then processes them but always hangs at the end on whatever amount of updates there are , 5 of 5 for example.
The task manager shows nis.exe using 100% CPU at all times, no other programmes are affecting the CPU use.
I have the same issue with scans, they take hours to run are use 100% CPU.
If i stop all norton products running my CPU drops to about 1%
I have tried the norton removal tool several times on each pc, same result on reinstall.
All 3 pcs are in good working order.
Running internet security version 22.9.1.12 on windows 7