You are right but beware, intermittent electrical issues can be a hair puller, even for the dealer. If it quits completely, that would be the best-case scenario.
The dealer is a new thing with me that I guess I have to remember. I have been turning wrenches all my life and I better readjust my thinking.
Anyway, if you want to get adventurous, there is a ground wire for both horns and if that’s not it, there is a smart junction box with a non-removable horn relay in it, with logic control. They may have to replace it.
I wish you well!