I found something interesting, although probably not groundbreaking! It maybe confusing as I'm going from memory without notes.
I ran a set of engines in a new consist with the phone app (call set #1), along with another set I'll call set #2 with the remote. There were some anomalies going on that I didn't understand but both consists ran. We took a break and after(with a cycle of power) we started another session. Set #1 just happened to be a pair of engines already created in the remote, but with the opposite engine in the lead. I ran that set #1 with the remote in the first session and running in reverse, the rear engine would sound the horn. I started running the second session and had created the consist in the app in the opposite positions and the lead sounded the horn.
So we ran the consists again on a third session and to my surprise, the front engine would sound the horn using the remote, which still showed the opposite positions. If that didn't surprise anyone we had to cycle the power to swap out consist engines in set #2 and when I restored the power once again ( fourth time), both engines in set #1 sounded their horns!
So how come with each session did the consist swap what engine would sound the horn? Was it from different devices and old lash-up builds confusing the system?