My book live 3TB abrupt data-loss?

There was nothing out-of-the-ordinary when I shut down my “notebook” and switched off my my book live 3.0TB personal cloud last night, except when I discovered this morning, that nearly 1 tb of movies were missing. an entire mesh of folders and subfolders so unfortunately just disappeared over the course of the night. I suspect it could be a corrupted file-index (by theory) though I have no idea where to start, to recover. Would someone show me how this data could be recovered please? Thank you!

Hello, have you tried doing a power cycle? If you access the dashboard, do you still have the same amount of free space?