[Joe K]

Um. That part establishes the "ground" between the horn body and the headlight bar. (The serrations "dig" into the paint and establish metal to metal contact - plus preventing relative motion of the horn)

Horn body grounded is not part of the electrical equation of the horn. The blue/yellow supply wire feeding the horn is very carefully insulated and the yellow wire coming from the horn to the steering column equally as insulated. The horn blows when you push the button grounding the yellow wire and completing the circuit.

SOMETHING connected to that yellow wire is causing the problem.

More likely and as Barnstuf was indicating, your horn/light switch problems were more likely caused by quality issues connected with the parts.

Joe K