I ment I closed all the apps from running. Doesn’t matter cause I got stutter back. Meh.
Ok guys... I come back to let you know my experience.
I write a little summary of all the story. I bought at the day one an Apple Iphone 12 Pro Max 256 gb. The problems I had SINCE THE BEGINNING were the stuttering when closing apps. In some cases (many times a day) it was going to the multitasking page instead of closing the app and this was really annoying. Moreover I had a video/audio out of syncro by rendering a video recorded with the phone itself (a few minutes) with Imovie. Also in imovie it wasn,t able to choose the photo and video in the "adding" page. A kind of "freezing" that you were able to solve by making a scroll down and going back up (crazy!!). I followed apple support's advices step by step starting by restoring ios in recovery mode (by itunes) till creating a brand new apple id to avoid that some data coming from my account could have been corrupted, but with NO SUCCESS AT ALL. The stuttering was present from the very beginning of everything i was doing with the phone. Then I asked to some friends which bought the same model but 128 gb of storage. No stutter at all, no problem at all, everything super smooth. They seemed to be different models!!
So i became to think about hardware problem and You all know that I went to the apple store asking for a swap unit. The guy laughed at me when I asked for a swap unit. He didn't want to swap the phone and just told me to go away because it was 100% software problem to be solved by an upgrade. But I didn' trust it and since i bought (as for fortune!!!) the phone on amazon, due to christmas time I had time till 31 Jan to send back the phone, obtain a refund, and then buy a new phone. And that's what I did. Yesterday I got my new phone from Amazon. I took the 128 gb storage. It has been two days since i am testing it and what happened just right after each test and reset, NEVER and I say NEVER happened in two days. Everything is smooth, imovie is working PERFECTLY, and i am really sure i went through this nightmare...!!
So...my BIG ADVICE IS: ASK FOR A REPLACE UNIT. That's what i did and that's how i solved this problem. I know there are many people here who think that it's a software problem. In my opinion it has been an hardware problem since the beginning and this new unit claryfied that I was right. If you want to wait for some update you're free to do it. It's your money, it's you time so you can waste it as you want. I decided to go on with my convinction an I was really right. It seems I have a new phone, very smooth and very fast.
The differences between this unit and the previous one were that the previous one was 256 Gb of storage and this one is 128 gb (like my friends units) and also the previous one came with 14.2 so I had to update to 14.3 This unit had 14.3 already installed.
Was it related to internal storage? (maybe apple has defective 256 storage memories)
Maybe
Was it a problem of the update from 14.2 to 14.3?
Maybe
I don't know, but with this unit I DON'T HAVE ANY KIND OF PROBLEM. It's everything PERFECT. If something will change I will honestly let you know. But for now in two days of massive use NOT A STUTTER AT ALL.
With the previous unit I had stutter Many many many times, impossible to not notice it.
So, again, my advice, coming from my personal experience is: ASK FOR A REPLACE UNIT.
Hope not to come back to talk about this again!!!
Bye to everyone!