Acme plugin and its dedicated ssh keys

[keeka]

I am setting up the acme plugin and using the 'sftp upload' and 'ssh command' actions.
I configured some actions, activated the plugin and an acme staging account.
I noticed the acme generated ssh rsa pubkey (that I'd copied to the remote hosts) had been regenerated at some point. This obviously caused the automations to begin failing.
What changes in the acme config trigger ssh keys in /var/etc/acme-client/sftp-config/ to be regenerated?
Many thanks.