M8 ignition switch stays in Accessory when off

[fleetmechanic]

2017 FLHTP with about 5K miles.  Just today when the switch was turned off we noticed the gauges and taillight
stay on just like Accessory mode.
I used the alignment too to make sure the innards were right.
HD Electronics manual was no help.

[Coyote]

Disconnect the battery for a bit and see if it clears up. May be the BCM.

[fleetmechanic]

I did that before I read your reply and it did clear it for now.  I'll keep an eye on it.
Thanks

[fleetmechanic]

Went back after a half an hour and turned it on and off. Same problem.
Is BCM failure a thing?

[fleetmechanic]

Anyone seen failures in ignition switches on '14-later fairing models? 
We have one on a '17 that delivers accessory power in the off position.  Disconnecting the battery only clears it until the next use.

[fleetmechanic]

Found the problem. The rider had turned back from heading to a funeral complaining that the airhorn
was blowing randomly while riding down the street. I substituted an amp of a different more reliable brand and then had no power to the siren amp. Once the siren button was pushed that's when the Ignition switch off setting became converted to accessory mode.  Each time I disconnected the battery it would clear until the siren was tried again.
I then noticed that the rider had disconnected one lead of the two speaker wires and it was hanging down and touching the steel body of the speaker driver that is grounded to the engine guard and frame.
This was sending a ground fault to the BCM. Reconnecting the speaker and replacing the amplifier fixed everything.