NIS using 100% cpu

PC has been getting very sluggish, I’ve turned off idle time optimiser but over several hours NIS.exe cpu usage climbs to 100%.
I have removed NIS from the performance monitoring exclusions but Norton still gives no high cpu usage alert for NIS, I must go into windows resource monitor to see it.

PC is running a core i7, 16G ram, SSD hard drive so i dont think lack of resources is the problem.