btrfs send failing, empty stream is not considered valid

[Massimo-B]

Hi, recently a remote ssh source is failing:

pro:/mnt/btrfs-top-lvl/volumes/root
=== pro:/mnt/btrfs-top-lvl/snapshots/root/root.20230919T072328+0200
!!! /mnt/local/data/archive/pro/root/root.20230916T010500+0200
!!! Target "/mnt/local/data/archive/pro/root" aborted: Failed to send/receive subvolume
!!! /mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200
!!! Target "/mnt/usb/mobiledata/snapshots/pro/root" aborted: Failed to send/receive subvolume

Looking closer with -vvv:

[send/receive] checking target metadata: /mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200
ERROR: Failed to send/receive subvolume: pro:/mnt/btrfs-top-lvl/snapshots/root/root.20230919T010500+0200 [/mnt/btrfs-top-lvl/snapshots/root/root.20230918T184301+0200] -> /mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200
ERROR: ... Command execution failed (exitcode=1)
ERROR: ... sh: ssh -i '/root/.ssh/id_ed25519' -o compression=no root@pro 'btrfs send -p '\''/mnt/btrfs-top-lvl/snapshots/root/root.20230918T184301+0200'\'' --proto 2 --compressed-data '\''/mnt/btrfs-top-lvl/snapshots/root/root.20230919T010500+0200'\'' | mbuffer -v 1 -q -m 6% | lz4 -c' | lz4 -d -c | mbuffer -v 1 -m 2% | btrfs receive '/mnt/usb/mobiledata/snapshots/pro/root'
ERROR: ... empty stream is not considered valid
ERROR: ... failed to check target subvolume: /mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200
ERROR: ... Command execution failed (exitcode=1)
ERROR: ... sh: btrfs subvolume show '/mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200'
ERROR: ... cannot find real path for '/mnt/usb/mobiledata/snapshots/pro/root/root.20230919T010500+0200': No such file or directory
ERROR: Error while resuming backups, aborting

What is broken, what can I do?

[Massimo-B]

--compressed-data and --proto 2 not supported on the remote machine.