2012 horn problem

A while back, one of the horns on my 2012 failed. The diagnosis was pretty easy: the wire rotted through a few inches from where it connected to the low-pitch horn. I bought a prewired connector (i.e., a pigtail with the Y11A1 connector) and spliced it in. Seemed to work fine, the only problem being that the crimp connector was imperfect because the wires were two different gauges.

But the same problem came back this past week. I figured the crimp had failed, so I opened things up and re-crimped. It didn't help.

I then noticed that the... I don't know what it's called. A disk around the circumference of the horn... is loose. It rattles if I touch it, while the same thing on the other horn is just fine. Is it safe to assume that this is the problem and that replacing the horn will fix it? Or can that part simply be loose while the horn still works?

I can try getting a video of it, but the space is very tight.

 

Well, I tested the horn and got 12v. So I ordered a replacement.
Opened things up but had trouble unscrewing the old horn (using a ratcheted offset screwdriver). Because I could barely get my hand in, I thought I should unbolt the hood latch catch. Got the 1st bolt off, but the second sheared off. Great.

So I made an appointment with Toyota. I don't know how I can get the remainder of the bolt out of the hole without removing the front, and I've never been good at broken-bolt removal anyway. Never did manage to replace the horn.