Stovedude

I bought a 2008 Express 2500, which used to be a handicap van. The door locks seem to have been reprogrammed, because they are definitely not acting normal. In Park with the key on, they will unlock every time I press the brake pedal. Also, when I open the door with the key on and running, everything locks and then the driver's door unlocks. That part might be normal, but it's so annoying and it makes me worry about getting locked out. Sometimes everything locks. I have it set to Lock With Speed, which works fine, but there are no options to turn off the locking, only the unlocking.
Does this sound like a BCM problem, perhaps needing a reflash or something? I don't think any other modules have been added, alfhough they did cut a yellow wire to the steering wheel air bag and spliced 2 wires into that (not sure where they go). Thx.