Stock alarm sounding issue horn blaring for no apparent reason

I purchased this car 1 week ago. On three different occasions when the car is armed and locked the horn starts to sound in a long not stop fashion. Not like a horn honking on and off. This usually happens a few hours after the car has been armed and I have only noticed it while the car in on my slightly slanted driveway. The only way to get the horn to stop is to remove the negative battery cable. The key in the door does not work nor The key fob does not work to stop the horn from blaring. I removed the fuse for the horn under the hood and now there is no horn sound. Last night at 2:00 a.M. The horn started once again and I also noticed the lights flashing inside of the car until I removed the battery cable.

I brought the car in to a local mechanic that only works on Fords. Not the dealer. He could not pull any codes and neither could he get the car to recreate the horn blaring condition.

Is this an issue that can be fixed? May it be an alarm control module? It seems this part is discontinued. Can I bypass the alarm completely and have an aftermarket alarm installed or simply have no alarm at all? I would like to have my horn back and no alarm at all. Thank you. Jim