My keyless entry on my 1998 subaru outback is unlocking the drivers door on its own!??

I recently purchased a 1998 Subaru Outback! Initially, I needed to get new batteries and reprogram the keyless entry, which I thought I successfully did. However, the car seems to mysteriously unlock itself. I thought it might be me accidently hitting the button in my pocket etc. but I have done several tests the last few evenings being very careful to make sure the keyless pad was not touched and yet the drivers side door is unlocked the following morning. Any suggestions?? Thanks!