Alarm Sounding randomly? 2015 Rav 4

[Sioo7]

I have a 2015 Rav 4 invincible and it the past week the alarm has gone on randomly multiple times while parked up. initially after 20 mins of sitting around. 

Ive checked the Battery status and it displays a healthy 12.3 volts. 

I have removed and cleaned up any signs of corrosion on the negative connections to the Battery and body. Also the positive terminal. since cleaning the alarm did not sound till the 8th hour , a much longer interval than prior to the clean. 

Other checks:

The hidden vehicle status display on the head unit is also reporting 12.3v.

The only way i can set the alarm now is with the interior sensor turned off using the button in the overhead light.

Ive checked the whole car for critters and carefully vacuumed the dust out of the sensor. 

Im now at a lose as to what is going on. 

My thoughts; have i masked the issue by cleaning the Battery connections. Possible early vehicle battery failure? is it that simple just change the battery?

Hood switch i have ruled out as i would expect the alarm would still trigger if this was the issue even with the internal sensor turned off?

Before i start substituting the interior sensor has anyone found the source of the issue?

Thanks for your advice. 

Si