Linode specifically takes a really long time to propagate DNS changes out to their nameservers (relative to other DNS providers). Last I checked, there's a note at the bottom of the DNS management page that states:
Changes made to a master zone will take effect in our nameservers every quarter hour.
That means after certbot writes the TXT record to your zone, it needs at least a 15 minute sleep time before it attempts to finalize the order. So up that propagation seconds value to at least 900 and try again. In my own personal testing with Linode, I'd still fail occasionally at 15 minutes and upped my own delay to 17 minutes.