fps drops from 50 to 15 when I cast skills and the problem started to occur after markarth update . anyone got any ideas what causing this?

here's a clip for reference:
https://streamable.com/pux3cv

also I've noticed sudden CPU spikes happening that happens every 15-20s while being idle in the game.usually it jumps 25% to 75-80% cpu usage and I'm using all of my cores which is 4.idk if it got anything with my problem

system specs:
Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz (4 CPUs), ~2.2GHz
8192MB RAM
DirectX 12
NVIDIA GeForce 940M 2gb vram
Intel(R) HD Graphics 5500 integrated