1998 Ford Windstar's sporadic alarm

So…I just [today] replaced the battery in my 1998 Ford Windstar GL and over the past few days, my alarm is randomly going off. As in…there seems to be no external influences and the alarm triggers and starts blaring. Each time this happens, the alarm has been armed. To remedy this problem so far, I’ve just been leaving my car unlocked–but I’m not so keen on doing that indefinitely…



Any ideas on why this could be happening? Thanks!!

Is this the factory alarm, or an aftermarket alarm?

This is the factory alarm – thanks!