Vehicles : "Engine on" was drop 5-10 fps.(I think it dropped more in a long time.)
Weather : Rain was drop 5-10 fps.
Sorry my bad English :)

Does anyone else feel like hitching is occurring more on servers with more players? It definitely feels like it.

The fps is dropping to near zero any time more then two shots are fired when two players are in close proximity. This has occurred in empty servers all the way up to full servers. It began after Tuesdays patch. I even saw it happen firing at a zombie with two quick shots from a double barrel. It really makes the game hard to play when you can not interact with other players and know what the game is going to do.

Could it be related to the update to the cursor for close melee combat affecting gun stability?

I also noticed on more then one occasion when the frames drop in close gun fights multiple red alerts pop up all at once if hit: my legs are broken, I'm bleeding , my arms broken. 5 or 6 in total but I can not remember the other maybe repeat alerts. If your legs did break during frame drop or your arm broke you will still be able to walk shoot even if everything's broken at once. It's like your legs/arms were never broken weird

It definitely occurs when 2 players are firing at each other in close proximity.

I don't think it's related to the melee cursor as the melee cursor does not show on 1st person servers and that's where I witnessed it happen.

IMO I think it has to do with the dynamic lighting that was tweaked in the latest patch.
I was watching "deadlyslob" stream on twitch and witnessed it happen to him too.
He mentioned he's pretty sure it only happens with unsupressed weapons (meaning it probably has to do with the muzzle flashes, which is linked to the dynamic lighting tweak)
I have not tried reproducing it with supressed weapons.

Possible lighting from muzzles or sound files causing fps drops, video by deadlyslob - https://www.youtube.com/watch?v=_DUJOm0lKn8

Whenever i shoot in close proximity with another play i get crazy fps drops, here is a video where it happends, video by DeadlySlob
https://www.youtube.com/watch?v=_DUJOm0lKn8
Skip to 4:46 to see it happen in action

I have the same problem! Whenever im in novy sobor police station and there is a guy i get horrible fps drops.

Hey guys, my friends and I recorded this (along with an fps counter) it may be helpful for the developers! :D

https://gfycat.com/FondFatherlyAndeancockoftherock