bad fps on 9950x3d

i have a 5080 a 9950x3d and a 32gb ddr5 6000mhz ram. Ever since I got my 9950x3d Ive been having troubles in fortnite with fps. What I have worked out is fortnite is not using the correct cores causing me to have terrible fps, when I hop on x3d mode capping me 8 core I get a 400 fps boost and run flat 240 the whole time. While I could just do this it ruins the help point of having a dual ccd ( I stream ) anyway is anyone able to help me out?