[question] snapraid-btrfs sync failure

Hello,

couldn't find a better avenue to ask the question. Probably missing something very obvious. I've set up the system as described in self-hosted/perfectmediaserver. Two disks - one data (BTRFS), one parity (EXT4):

/dev/sda1 on /mnt/parity1 type ext4 (rw,relatime)
/dev/sdb1 on /mnt/data1 type btrfs (rw,relatime,space_cache,subvolid=256,subvol=/data)
/dev/sdb1 on /mnt/snapraid-content/data1 type btrfs (rw,relatime,space_cache,subvolid=258,subvol=/content)

/etc/snapraid.conf:

# Parity location(s)
1-parity /mnt/parity1/snapraid.parity

# Content file location(s)
content /var/snapraid.content
content /mnt/snapraid-content/data1/snapraid.content

# Data disks
data d1 /mnt/data1

# Excludes hidden files and directories
exclude *.unrecoverable
exclude /tmp/
exclude /lost+found/
exclude downloads/
exclude appdata/
exclude *.!sync
exclude /.snapshots/

Now I can't make snapraid-btrfs sync complete. The output of sudo snapraid-btrfs --quiet sync:

Self test...
Loading state from /var/snapraid.content...
Scanning disk d1...
WARNING! All the files previously present in disk 'd1' at dir '/mnt/data1/.snapshots/41/snapshot/'
are now missing or rewritten!
This could happen when some disks are not mounted
in the expected directory.
If you want to 'sync' anyway, use 'snapraid --force-empty sync'.

I've tried various operations so there's a bunch of snapraid-btrfs snapshots created which I won't list. However, the last one - 41 - is where I would expect to see it:

dm3@nas01:~$ sudo snapraid-btrfs --quiet ls | grep snapraid
41  | single |       | Sun Sep 26 21:42:56 2021 | root |         | snapraid-btrfs sync       | snapraid-btrfs=syncing

The versions are as follows:

dm3@nas01:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 21.04
Release:    21.04
Codename:   hirsute
dm3@nas01:~$ snapraid --version
snapraid v11.5 by Andrea Mazzoleni, http://www.snapraid.it
dm3@nas01:~$ snapper --version
snapper 0.8.15
flags btrfs,lvm,no-ext4,xattrs,rollback,btrfs-quota,no-selinux
dm3@nas01:~$ snapraid-btrfs --version
snapraid-btrfs 0.14.0+git

Would be grateful for any help and pointers!

automorphism88 / snapraid-btrfs

[question] snapraid-btrfs sync failure #20