Underperforming 9900k

Hey guys, first time posting in here, hoping someone can steer me in the right direction.

Today i upgraded my 9700f to a 9900k chip, it was a straight swap with no issues, but the 9900k seems to be underperforming, judging by its geekbench 5 score (8100, should be closer to 8800). Is there anything that could be holding it back? perhaps my system is configured for the old chip and is not utilising the new one perfectly?

My brother built this machine for me so it might be something obvious to you guys, but alien to me.

Thanks for any help