I didn't know that unlocking at the trunk disabled the alarm. I do know on my 1987 300SDL that relocking and then unlocking again at the passenger door always stops the alarm. My car had been sitting for years when I got it. I didn't even know it had an alarm until I set it off Anyway at first it seemed like it would go off without any rhyme or reason. I noticed many locks were stiff and seemed slow to open. Things are moving better now as I use it everyday and I have lubed a few things. My alarm hasn't gone off in a week. Is it possible that your mechanical pieces need a little lube?