Failed to create encrypted root directory

Installed Cryptomator. Pointed it at a network share via SMB. Mapped that to a Windows drive letter (V). Opened it successfully and started moving data. 4Tb later my machine is crawling and saying the copy is to a ‘disconnected network share’ I stop the copy. I have a directory structure on the target disk, called ‘d’, with two-letter subdirectories. Lots of them. With .cr files in them. However Cryptomator does not recognize this as being a Vault and says it ‘failed to find an encrypted root directory’. How could this happen? And now what? Has 4Tb of data been moved into a useless state?

Managed to recreate vault.cryptomator file by downgrading to v15, and using recovery key. Can now 'see vault" in v1.5, but whatever I try to do to it fails with ‘disconnected drive’ errors. Upgrading from there to v1.7 gives ‘aultKeyInvalidException: Failed to verify vault config signature using the provided key.’ I feel like I’m so close, yet so far away.