Strange Case of Overactive Horns

[magwakeenercew2jh]

Seems like the horn circuit is about the most simple one on our trucks.

Horn grounds itself and the + (green) goes thru the firewall at the fuse block and then under the dash to the horn relay. Three wires to the horn relay:
Red is always hot, the green that goes thru the firewall, and the black that grounds at the horn button after making it's way there via the banana-shaped
"Directional Signal Connection".

I've had the horn button fabbed and installed for a while, had the wiring harness (new) installed for a long while (like, a year). Although I haven't really been idling the motor much
because I'm running straight out of the headers for the time being, everything horn-related has worked well while it was at the shop ....and for the last week that she's been home.
I drove her home the 1/4 mile from the shop with open pipes just to get here. And, I've moved the truck in and out of the garage to do little stuff while I wait for the exhaust appointment.

But today, I started the truck and let it idol up to temp. the frigging horn started to honk. Because the last work was at the horn button, I pulled that off quickly and "un-grounded"
inside the steering wheel. Nope!!!!

Hoooooonnnnnnkkkk! Steady, neighbor raising, yelp from the horn. (And I live in the country)

I jumped out and pulled the green horn wire. Which sparked, showing me, if I didn't already know it, that it was getting juice with no jey on, no horn button pushed, nothin'

I waited about three minutes while I thought about it. Went and got the voltage tester light. Yup, drat'ed unwanted juice at the disconnected green wire.

Waited another three minutes or so, checked again. No juice at the green wire.

Re-connected the black ground wire at the column (horn button), connected the green wire at the horn. Pushed the horn button. "Honk!" Un-ground (un push) No honk.
Push the button. "Honk!" Cool. Just the way it's supposed to work.

Drove into the garage and let her idol for a couple of minutes. Shut down and got out and did a few things.

While I was about 100 feet from the truck....."Hoooooonnnnnnkkkkkk!"

I had to go pull the green wire. Tested for juice...of course, there was juice at the green wire. Waited until three minutes later, no juice.
So I connected the green wire again. Perfect honking again from the horn button.

I walked away.....Three minuted later, auto-honk again.

Relay? I've had a little problem at the fuse block since the build. Maybe a grounding there? It seems that would be less likely...Although next week my M&H fuse block
and under-dash harness will be here (All the rest of the harness' are new M &H), I suspect the horn relay. Obviously, the green is getting juice. Obviously, the red is hot to the relay.
I'm convinced that the horn button, ring, spring, etc. are not the culprit, as when all is working, the grounding starts and stops on "button command".....

Am I thinking straight on the horn relay? Can they fail in the "honking" position?

Any tips?