With the CarHorn mod I have created: https://steamcommunity.com/workshop/filedetails/discussion/1748971864, there is a strange bug that I am trying to resolve. I am thinking is a core issue at this point, because I cannot seem to find any logical reason for it otherwise.
Basically when a vehicle takes damage enough to cause the damage sound to be played, any "toot horn" will play the horn sound as well as the crash sound (Example.