python 881xp sensor tripped at same time

I'm confused by this problem. I had my Python 881XP pulled from my old car and reinstalled in my new car last week. Everything works perfect, there are no problems, I'm just giving the background.Yesterday at 8:45, my remote beeped at me with the 'SENSOR' warning. I work nights but keep this close by so it woke me up, and I ran out to my car to find no one around and nothing out of the ordinary except the flashing LED when I started the car (2 flashes). I thought maybe someone bumped it as it's in a public garage, so I didn't give it much thought.. until this morning. Same exact sensor, same exact time. There are no trains or anything near me, so I'm stumped. Anyone have a clue why this is happening? Other than standing beside the car at 8:40 tomorrow, any tips on my problem? Thanks!