I also have had this issue with my iPhone 12 Pro Max since day one (literally “day one” as pre-ordered, etc.). Eagerly updated every software update since, in the hope that it would be fixed but alas here we are at IOS 14.4 and it still has not been addressed. Yes, it’s not the worst problem to have in the world but after three months of owning the phone I’m becoming increasingly annoyed at this - at £1,099 it’s comfortably the most expensive phone I’ve bought and yet the user experience has been nowhere near as smooth as any of my other iPhones (probably had half a dozen different iPhones since iPhone 3G). The hype around it having “the fastest chip in a smartphone” seems completely ridiculous when you can only have ten or so apps open at once before getting this ugly stuttering when closing an app (or as others have said, the ‘open apps’ menu appears when you don’t want it to). I’ll persevere, but so far I really don’t feel the phone has been worth anywhere near the cost as the user experience (in my opinion) really is affected by this - we also had the stuttering issue when beginning to type out iMessages for the first few weeks, although that seems to be fixed now. Please fix this, Apple - I really don’t want to be looking elsewhere for my next handset...