2012 CX-9 uncontrolled honking

My 2012 CX9 has just started to behave in a manner that forced me to disable horn. The issue is that when the car is on, it can produce low honk sounds the same as when you lock your car with the remote but in more inconsistent way as if there was some sort of shorted circuit. When it does it, the light indicating lights-on flashes and a ticking sound can be heard in the cabin. My mechanic couldn't really tell me what this was and pointed out that it could be something wrong with the immobilizer. Authorized Mazda service sent me back home with nothing. Anyone faced a similar issue?
 
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