macOS Samba Issues (User shares OK, disk shares result in failures!)

Background: I had another thread open (which I've now deleted) as I thought the smb message I got at the time was relevant. 

Short Story:

Previously I used to backup directly to /mnt/disk1/Backup/XXX and this seemingly worked just fine.

However a few months ago now these started to regularly fail, especially when backing up my Mac's boot drive which has some very long and deep file paths.

After some testing I found out that going via the user share "Backup" works what appears to be absolutely perfectly with only minor errors (i.e. the backup completes compared to failing completely).

If I move back to "/mnt/disk1/Backup/XXX" things start to fail again. This applies to both rsync and CCC. On some occasions the SMB mount point is actually ejected (along with all the others).

These are the errors that I can see in syslog during the backups:

Jun  1 18:34:13 TOWER-NAS smbd[24819]: [2020/06/01 18:34:13.839583,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:34:13 TOWER-NAS smbd[24819]:   lp_bool(no): value is not boolean!
Jun  1 18:35:21 TOWER-NAS smbd[29422]: [2020/06/01 18:35:21.358475,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:35:21 TOWER-NAS smbd[29422]:   lp_bool(no): value is not boolean!
Jun  1 18:37:52 TOWER-NAS smbd[9607]: [2020/06/01 18:37:52.683904,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:37:52 TOWER-NAS smbd[9607]:   lp_bool(no): value is not boolean!
Jun  1 18:38:13 TOWER-NAS smbd[11372]: [2020/06/01 18:38:13.076973,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:38:13 TOWER-NAS smbd[11372]:   lp_bool(no): value is not boolean!
Jun  1 18:39:28 TOWER-NAS smbd[17024]: [2020/06/01 18:39:28.851723,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:39:28 TOWER-NAS smbd[17024]:   lp_bool(no): value is not boolean!
Jun  1 18:42:19 TOWER-NAS smbd[31108]: [2020/06/01 18:42:19.593322,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:42:19 TOWER-NAS smbd[31108]:   lp_bool(no): value is not boolean!
Jun  1 18:42:52 TOWER-NAS smbd[429]: [2020/06/01 18:42:52.433449,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:42:52 TOWER-NAS smbd[429]:   lp_bool(no): value is not boolean!
Jun  1 18:43:18 TOWER-NAS smbd[3406]: [2020/06/01 18:43:18.728991,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:43:18 TOWER-NAS smbd[3406]:   lp_bool(no): value is not boolean!
Jun  1 18:47:55 TOWER-NAS smbd[429]: [2020/06/01 18:47:55.535195,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:47:55 TOWER-NAS smbd[429]:   lp_bool(no): value is not boolean!
Jun  1 18:48:58 TOWER-NAS smbd[30389]: [2020/06/01 18:48:58.740944,  0] ../../lib/param/loadparm.c:414(lp_bool)
Jun  1 18:48:58 TOWER-NAS smbd[30389]:   lp_bool(no): value is not boolean!

The problem with going via the user share is that the performance is much slower.

These are the SMB settings at the moment:

veto files = /._*/.DS_Store/

case sensitive = yes

#unassigned_devices_start
#Unassigned devices share includes
   include = /tmp/unassigned.devices/smb-settings.conf
#unassigned_devices_end

[global]
log level = 0
logging = syslog

Enhanced macOS interoperability: Yes

Enable NetBIOS: Yes

Enable WSD: Yes

I originally thought it was something to do with macOS, but given it works via a user share and not a disk share then that points back at UnRAID.

There is nothing else in the log that hints at any other problems.

Cache_dirs has been tried on and off as well as at different search levels.

I've also tried 6.0beta1 - same problems.

Why on earth would the user share but not the disk share work OK!?

Thanks...!