system hangs at boot - LUKS /home/ problem(?)

[Fulbert]

Hello! Seeking some help/suggestions to solve a problem preventing
my system to boot up, which was working properly up to guix 9b84b36
(21 mar 2024) (note: I confess that my system is not totally pure).

Starting with guix d5f857a (22 mar 2024) up to my latest guix pull
with 1415ea7, the **system hangs during boot**, and it does before
anything is written to /var/log/messages. So, using a video capture
of the screen at boot, I was abble to catch :

#+begin_src boot
shepherd[1]: Exception caught while while starting device-mapping-luks-homes: 
(unbound-variable #f "Unbound variable: "S" (bytevector?) #f)
#+end_src

… which appears to be the culprit ?!

follows a long list of "shepherd[1]: Service XXX depends on YYY" and
then
#+begin_src boot
shepherd[1]: The following services could not be started in the background: 
<follows the list of all services the system should start>
#+end_src

>From there : a blinking cursor and the only way out I found is
CTRL-ALT-DEL, which triggers shepherd to stop some services. After
that I have to shutdown using hardware button.

My system and its config.scm have not changed and I see nothing
relevant, related to LUKS/dm-crypt, in `guix pull -l`.

My LUKS is configured like so :

  (mapped-devices
    (list
      (mapped-device
        (source (uuid "<the uuid>"))
        (target "luks-homes")
        (type luks-device-mapping))))

  (file-systems
    (append
      (list
        […]
        (file-system (mount-point "/home")
                     (device (file-system-label "luks-homes"))
                     (type "ext4")
                     (dependencies mapped-devices))
        […]

Any help would be appreciated.