We had quite a few cases of this, usually we have backup. But few times we lost days of work.
Unreal gets very unstable when we use structs, function libraries or sometimes dispatchers.
Usually we get stuck with “cannot save” error due to “graph is linked to private object” and usually that object leads to such corrupted struct or function that just refuses to compile.
When we are lucky sometimes compiling troublemaking function fixes it all, but with garbled structs we do not have solution.