Hi men, I was in that situation for months and I already managed to get through those doors. I did it thanks to the advice of users. You have to be a little patient and meticulous. I assure you, if you do it, it will come out. My frustration was such that I recorded a video and uploaded it to YouTube. Starting at minute 3 it shows you the result of how you pass the door. 1 near the locked door press the Menu button, then triangle, to access photo mode (this apparently activates the Buffer) then exit with a circle. (Just doing this once is enough.) 2 you distance yourself from the door and run towards it and just before touching it (you are running towards it) quickly press the pause button and scroll to settings... then you exit normally from the menu. and Cal Kestis will appear behind the door. I hope you get it on the first try. (I did it after 4 or 5 attempts) I assure you that it works. As I mentioned, I'll give you the YouTube video that shows how I did it.
https://youtu.be/bwfCgchvm34?si=pTszJDq_aKsLEvrc