You probably have memory leak in some blueprint, it usually happens when blueprint gets corrupted.
So, first make backup of whole project. Zip whole project and move that file to another folder on same drive.
Now get something like TotalCommander, or use windows explorer. You need to find which blueprint file is corrupted. If you click one of them blueprint editor loads them all, because of dependency. And if one is corrupted it crashes editor.
How do you find offending flie:
Delete half of blueprint files, open editor and see if clicking on one of the mcrashes whole thing. If it does not, then it was one of deleted files. Restore half of them. Check again, repeat until you find corrupted file.
But sometimes crashing happens because you made some really strange material, or did some weird thing with pointers (References).
There are also error logs for editor, maybe something in logs can give you some clues.
Ps. MAKE backups, some version control system, or good old zip and backups every time you make major changes.