I have encountered this issue. I think they know at least a bit about it, because in the dev updates they say they will address “multiple screens functionality” with sim update four, if my memory serves. I’m not sure if they specifically mean performance, but that’s what I’m hoping for as this issue is pretty annoying.
Also, its only been from the latest update for you? I’ve always had this issue but then again, you have much better specs than me so I’m not sure. Hope they can fix this!
Cheers.