Disable internal motion alarm (Avensis gen 2)

[wassah]

Hey all, just got a gen 2 Avensis (2004) and really like it except for the internal motion alarm that goes off every now and then. I'm wondering whether there's a way to disable it more permanently? From what I've found I can press the button by the roof light, but that only disables it until I unlock the car again. I can also lock the car mechanically, which is supposed to leave the alarm deactivated. However, I would like to just leave my car and lock it with the remote without having to worry about setting off the alarm, so I'm looking for a way to disable it more long term. We've already accidentally set it off 5-6 times, and I strongly believe this alarm will cause more harm than good.