Missing scenery after restarting the program

[LobanychPlay 0]

I am a beginner animator, and recently I ran into a problem in Mine imator that was not there before. After each restart of the program, my scenery everywhere become invisible, and I have to create new ones, but each time I make different territories of the world, and in the end I have to start all over again. I have to do all the animation without restarting the program. What could be the reason for this error?

Edited September 24, 2019 by LobanychPlay

[Korbs 104]

This appears to be a problem with someone else as well where only doors came back! 

[LobanychPlay 0]

2 hours ago, Korbs said:

This appears to be a problem with someone else as well where only doors came back! 

In addition, I have this problem both on a PC and on a laptop