I don't know, but some other brands, like Motorola, also have this issue. And I think Samsung should fix this problem in the next software update. In simple words, what I understand is that they can't control the heating .
Because of the vapour chamber cooling system. If your device gets too hot, the cooling chamber turns heat into vapour, and because of this, you notice some moisture or droplets of vapor in the camera.
I think this is the bug. If the problem is in the GPU the f55 doesn't work properly mine works fine. I also notice lag but only when the phone is warm; otherwise, it works fine