Hi, thanks for the tip. However, this frame drop also occurs while I am off duty. For example, just now I started the game as Trevor, spawned a police car I wanna use during the patrol and it happened during spawning process. It is really, really random. As addition, my settings are now med-high and usage of vram as per GTAV (I know it is not true but give the idea) is about 1830mb.
In addition, I noticed that frame drop to 20fps always happens when I respawn in a hospital after being killed on duty. I am using EUP 7.2 if it could help anyone.