I decided to upgrade the Soyuz spacecraft with a launch vehicle again, and I decided to fix the docking mechanism, removed the Soyuz from the rockets, and then inattention played a role.
As a result, I went far with the correction, realized late that instead of saving a separate Soyuz spaceship with other names, I overwritten the save with rockets (in which I modified the fairing) and within a few minutes pressing the "Undo" button, the button disappeared. The rocket never appeared, the Soyuz spaceship was saved, but the mood was gone.
What can I say, if you need to fix a separate mechanism, rename it before saving.
P.s. Although many people will not be interested in this post, I do not know.
I feel you man, these mishaps push you back in time