It’s a week that I am fighting with annoying problem, I built many maps in order to create an animation.
At some point after I save it my Level Map disappear, there is nothing there anymore ALL GONE!!
Is this normal, is this the way UNREAL work, is this meant to be a professional tool at all???
Davide,
To be honest it doesn’t make sense what you described, since you mention an animation, but an animation of what?
A character? camera?
A few screenshot or better yet a video would clarify what the proble is, otherwise I don’t think someone can understand what the problem is.
Yes no problem.These are 2 frames of different sequence I exported with some effort.
Camera is moving and a Character I got form mixamo is dancing, is it a Halloween things I am working on.
Has happened 3 times that while I was rendering I experimented some crash after that when I reopened my Level Map I just have the geometry in the folder that I have imported with Datasmith, but the Map is gone, is completely empty a black viewport, so I had to redo everything form the beginning.
I am now on the 4th and really last try
Instead of “redoing everything” you should have backed up date inside your saved folder within the project. anything generated from the autosave feature usually backs up about 10 iterations of the whole thing in there.
also, do make sure you opened the correct map. it could be the engine re-opens a default blank map instead of the one you had been working on. nevertheless, the auto-save backups should help you should that not be the case.
Also “sto uscendo pazzo” si tradurrebbe meglio con “i’m going crazy”, just in case 
Hello thanks for your reply and for your grammatical correction, it was just an artistic licence.
Are you italian?
Anyway…
"Instead of “redoing everything” you should have backed up date inside your saved folder within the project. anything generated from the autosave feature usually backs up about 10 iterations of the whole thing in there.`"
Please explain I know very little about Unreal, where can I find this file and how can I recover it??
Cheers!
Uè, stiamo calmi 
Anyway, the loss of data might depend on the BuildData of the map that goes corrupter, I had the same issue for some maps, so my advice is to, as soon as the map is done, to create a duplicate, make sure that the BuildData is saved ( you can clearly see that beside the map name, and try to close-open it again.
Worst case scenario, try to put everything inside a BP, so that even if the map goes away, at least most of the job you did is not gone and can be drag&drop inside the scene in short time.
And yes, make sure that as soon as the project opens, the map is automatically loaded, or look for the map you created and try to open it, since UE4 default settings always open a default map.
What version of the engine are you using?
Super! e io che iniziavo a pensare male 
Thanks again is actually something I have done, I clone the map and Renamed it.
It did’t happen again, but it looks like it happens very often which is quite frustrating.
Could be a disk space problem or something relate to the Hardware (a laptop in this case)?
I’ll keep you update about my experience with the engine.
Thanks I will annoying you with a lot of questions…
Could be, since depending on how heavy the scene is, the GPU of the laptop might go nuts, and yes it can happen that it will also eat the hard disk memory ( this happens to me a lot when using Maya for example ), so keep an eye on the hard drive and see if you notice any changes.
Every time UE4 crashes a pop up window appear, so usually you can also see what is the cause, so that you’ll know what’s going on.
If something else come up, feel free to annoy
I speak several languages fluently.
Most of the times something like this happens you would also experience a crash. If you didnt crash but properly close the engine, then the scene and related files would either they’ll you they are Corrupt or whatever else the matter is would be reported within the verbose log.
You can actually pull up the log from the menu.
Window -> Developer Tools -> Output Log
Anyway, the Autosave files are located inside your project folder in the /saved directory.
You have several things in there, one being the copy of the /content folder with the files prior to the latest modifications.
The file path may be something close to /Save/AutoSaves/Game/Maps
All you have to do is copy the file (.uasset) back into your /content folder in the main directory of the project.
If you are wondering where the project files are stored, you can actually right click one and find the open in explorer/os option under the asset action sub menu.
For windows it’s usually c:/users/<username>/documents/<unreal projects folder>/<project name>
Either way, I would suggest a check disk on your laptop. Most of those types of corruptions are due to bad harddrive sectors or hard drive related errors - possibly caused by overheating, or HDD/SSD stress.