opnsense-bootstrap failing on AWS

[slavetothesound]

I ran the script 4 times yesterday on the official AWS marketplace image of `FreeBSD 12.1 RELEASE` just as described in the short instructions on github. https://github.com/opnsense/update#opnsense-bootstrap

I never saw an error message, but all 4 attempts resulted in a system that was no longer reachable via SSH or HTTPS.

Is there an undocumented step or trick somewhere that I might missing? Does it maybe change it's IP configuration from what is in the AWS control panel?

Edit:
The instance specs I was using were 't3.small' - 2 core, 2GB ram, 12GB SSD.
I tried it with 1 or 2 interfaces always all on the same private subnet (172.21.3/24).
Nothing in the system log to indicate success, new password or anything like that.
All requests timed out rather than being rejected.