[458 Spider] Alarm engaged by itself without locking on key fob

Hi all, upon quick test drive in a 2013 458 Spider with the seller, noticed something awkward after shutting the engine down.

The car’s alarm system would arm/engage by itself (long single beep; same as beep when locking car) within ~30-60 sec (despite doors in unlocked state) without locking on the fob (doors are unlocked). Opening the unlocked door (either side, driver's/passenger's) would sound off the alarm. The alarm could only be turned off only by pressing 'unlock' on the key fob.

Despite trying to lock then unlock again, the alarm would arm itself again (long single beep) without pressing 'lock' on key fob after 30-60 sec (doors unlocked) - opening the door would sound off the alarm.

This is the first time I've seen this alarm issue where it would arm itself despite unlocked doors, and the 5-6 other 458s (Coupe/Spiders) I've seen in person did not exhibit this.

Is this due to a setting in the car or is there something wrong with body ECU/electrical?
Any one experienced this issue before?

Thanks in advance everyone.

 

PS: There were no related warning lights on the dash. None of the alarm system failure prompts per the owner's manual.