This issue is described in more detail at [1]. Essentially, 'guix
deploy' is will happily load and start new services, as well as unload
obsolete services, but does nothing to restart valid services that are
already running.

I can assign myself to this issue. Just filing for tracking purposes :]

Regards,
Jakob

[1]: https://lists.gnu.org/archive/html/guix-patches/2019-06/msg00567.html