NexcloudPi crashes a couple of times week, Your data directory is invalid

You should disable automount if you decide to use uuid, can follow Mounting an external drive using UUID and fstab | Linux admin junior instructions.

It is more important however to find out why automount is failing, rather then changing the method of mounting the drive. Have you tried checking the connections and changing the cable?

Automount should work fine, unless you want more control over drive mounting or need to add more then one drive.