Cannot connect to Lightsail FreeBSD instance created from snapshot

I run in this problem with a production instance and also reproduced it with a newly created instance:

1. created a new Lightsail instance with FreeBSD as OS
2. tried to connect via web SSH → connected successfully
3. created a snapshot from the instance
4. created a new instance from the snapshot
5. tried to connect to the new instance via web SSH → connection impossible

When trying to connect, either from the web SSH or from my computer, I don't get any error message, it just continues to try connecting until it eventually times out.

I compared the informations about the 2 servers using aws lightsail get-instances and could not find any suspicious differences between the servers.

This is a serious issue, as I'm probably not the only one relying on daily snapshots for backup: it turns out they might be completely useless.