"Alarm Not Available" Solved!!!
For the past year (since I got the car) I was getting an "Alarm not available" message. After many troobleshooting steps, including removing the senors from the doors, checking for water damage etc etc, diagnostic tools (That were poing to a sensor 3, that I had no idea where it was, since there's supposed to be one on each door only. Maybe it meant Tilt sensor which is below the armrest console and had no intention of taking everything apart to look for it).
I had AlfaOBD on my phone and used it for various troobleshooting stuff. Downloaded new version and was playing around with it when I found out a new entry "Hypersonic sensor Enable/Disable". Had a go at it, then I had to do a proxy alignment (again through AlfaOBD) and now, no more error and no more double beeps when locking. Problem finally solved!!!