Locking 2003 Rav4 not using key fob

[amatty]

My RAV4 when locked with the key fob sounds the alarm sometimes after a while, so I have been trying to lock the car with the key on the drivers door so as not to set the alarm, but this only locks the drivers door and not the whole car or the rear doors at all.

If I leave the car unlocked  the alarm does not go off on its own - so this is how I have to leave it overnight so as not to disturb my neighbors.

All the locking and unlocking functions work fine from the key fob except that the siren sounds sometimes after a few hours.

Banging door panels etc does not set off the alarm, so I do not think the sound detector is over sensitive and I have cleaned up the Battery terminals and connections to the chassis and checked the Battery at 12.6 volts.

Any ideas please.