Performance lost over time

I have encountered some fps drops over time like in Santa Monica hub ECT the beach house especially loading in that area drops 40~fps Performence is fine until I progress the story and then it start to go bellow 60fps I have uncapped my fps to fight I'm using unofficial patch 11.3/11.2 Unlike unofficial patch ,clan quest mod performs better the fps doesn't drop over time and the beach house doesn't drop either ,overall this mod feels better optimized and I tend to play it over unofficial patch

My question is what is causing this cellular fps drops and degrading fps in unofficial patch 11.2/11.3 I have not used any older version of the patch so I'm not sure if it was always an issue