1998 Nissan Altima Unintended beeping and parking light fla

Perhaps once a month or so, while the car is parked in our garage, the horn starts beeping very regularly, like a truck that is backing up. When my wife hears that, I open my back door and I can see that the front left parking light blinks each time the horn beeps. Typically, this happens 3 or 4 times, within an hour or so. (I can't see whether the other parking light blinks.) Typically, there are perhaps 3 or 4 such sessions within 30 or 60 minutes.

My hearing is bad, so I don't hear the horn until I open the door. My wife hears the horn, but she doesn't remember this source from one occasion to another.

My auto mechanic found a Nissan document that explains how some part about 6-inches long inside each of the 4 doors and involved with the door lock is sometimes found to get wet after the car is old, and this causes problems. Nissan changed to a better replacement, but without opening up every door he cannot tell which doors have the old problematic part or the newer replacement.

If I KNEW FOR SURE that this is the problem, I would pay him to replace these parts --- there are other strange things that happen, perhaps from the same cause. (For example, in warm weather & I am driving slowly, sometimes all 4 door locks close of their own initiative, usually while I am using the foot brake.)

He tells me he would have to open up all 4 doors.
I don't want to pay him to take each door apart and discover that the answer might be something different, which might be very expensive to replace.