Does Unreal Engine 4 Need the soruce files, To work

So i been working on a project, with a player using run, and walk, and fire animations, ect.
-I saved these animations, on my desktop, to import them, but while cleaning my desktop i deleted them.
-Question being do i need the “original fbx exports” from 3ds max for them to work to unreal engine 4?

-Reason: I’ve been having crashes, constantly, and i have no idea why they are crashing. I thought me deleted the source files might be the cause for the editor crashing and ruining my projects.

-Also anyone else have this problem, where projects will just crash and they are ruined, for a long time?

They have some connection to source file(For fast reimport for example), but only for this purposes afaik. I’ve never kept source files and never had problems/crashes due to this

Do you think this might have something to do with it?
-I have a software that deletes everything that is not saved in the UE4 project files.
-So if its making adjustment to registry or anything like that, it is deleted.
-also sometimes i don’t click restore packages.

-sorry i’m really trying to solve this crashing problem it has wrecked countless projects of mine, that i have spent several days on. And i’m reluctant to spend more because i do not know what caushes the crash of certain projects.

I doubt it, but it always possible of course. I recommend to post crash logs and description of this problem in bugs section of AnswerHub