RealTehreal

First things first: if you don't have a backup, just for future reference: always have a backup of important data. This is a MUST, independed of VeraCrypt. Now to your issue: you can try to use the integrated backup header of your volume. It's an option before mounting. In case the main header of your volume got corrupted, but the backup header is intact, you would be able to mount your volume. If it works, you should create a backup of your data and start over with a new volume (and maybe a new...

Is it possible, that you actually have permission issues? How do you connect to the NAS in the first place? dav(s)+Linux always creates headaches... Greets

It's possible, that you removed your external drive before the copying process finished. This could also be the reason for the corrupt file system. But it's also possible, that the external drive had some issues. You could try to search the filesystem with data recovery tools. Maybe you're lucky. Greets

Your questions regarding system encryption should be covered by VC's documentation: https://veracrypt.fr/en/System%20Encryption.html The cache of your HDD should not compromise security. Data read from and written to a VC volume is only decrypted on-the-fly in RAM. That's why your HDD would never see unencrypted data from within a VC volume. Greets

You don't have to open both volumes. Just mount the hidden volume and you're good to go. Use your preferred file manager to determine the remaining space within your hidden volume. Greets

You cannot resize a VC volume the way you would do so with an unencrypted partition. VC volumes consist of your encrypted user data and quite a bunch of meta data. You would have to manipulate the meta data in a way, VC would use the remaining space on your media. Afterwards you would have to mount the volume without mounting the filesystem inside of it, resize that one as well, and hope that nothing bad happens. This would be quite error prone. Therefore, you should setup your new media device with...

You cannot resize a VC volume the way you would do so with an unencrypted partition. VC volumes consist of your encrypted user data and quite a bunch of meta data. You would have to manipulate the meta data in a way, VC would use the remaining space on your media. Afterwards you would have to mount the volume without mounting the filesystem inside of it, resize that one as well, and hope that nothing bad happens. This would be quite error prone. Therefore, you should setup your new media device with...

In Linux, you can mount such images as a loop device and then decrypt it with VC like any other storage device. Greets Edit: If it does not work, try using the embedded (or external) backup header. If it still won't mount, it's most likely too damaged.