While it doesn't happen every time, I've come across several occurances of the horn staying on, but gradually fading, only for it to just kinda come back later.
Ah, the " Ghost Horn of Sand Patch Grade " has returned. It was reported a few years ago with the SD40-2 on SPG. The horn would remain blaring, gradually fading away, but then return, like the Flying Dutchman, moaning in the distance, disembodied from any loco. Far as I know, the ghost horn was never laid to rest by DTG. You must have made it angry and now it's haunting you on CJP.