Glad to know it worked
So it was actually true that my application wasn't serving all the certificates needed. I was somehow confused by the name /etc/letsencrypt/live/scatologies.com/fullchain.pem, I was thinking it would contain all the certificate needed for verifying the host, but that's not true.
FullChain.pem is exactly that a combination of the domain certificate + intermediate, however depending on your system it may require (and I think ruby does) you to separate these out. There is not hard and fast rule about this so it's one of those things that needs to be figured out
Andrei