Recently added updates cause extensive problems

Hello, I wanted to get some more information regarding the new updates. While creating the project, everything worked fine for me when I was using 2019.x. One after the 2020.x update. I started having a lot of problems. Example: All objects in all scenes are visible. I started the game, changed the scene and suddenly these objects are not present during the game (I figured maybe some error in the code), but after turning off the game and returning to the 'scene' tab, these objects are not visible. After restarting Unity, I enter the same scene and these objects are visible.
I am asking for help in solving this problem, as it makes creation terribly difficult.