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:
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@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
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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.