It appears since about a month (first detection of the issue in our infra 13/12/2023, Tuleap 15.3.99.39).

SSHd does not seems to be able to restart when the container is restarted with the following error:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0640 for '/etc/ssh/ssh_host_ed25519_key' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
key_load_private: bad permissions
[...]

(Same for the other host keys).

It looks like it does not like the symlinks.