Passenger Door not auto unlocking?

[bmwzzzz]

Hey all!
Ever since I got my '03 Z4 about a year ago, the passenger door has never auto unlocked.
The drivers side door has no problem; hit the remote unlock button and it opens fine. In addition, the passenger door also locks along with everything else when using any of the lock buttons.

Any idea on what may be causing this issue? I find it strange that it does work in one case but not the other.

I'll note in case it is possibly relevant, the battery was dead for probably a year when I first bought it. That caused a number of other electrical oddities that I was able to solve with a code scanner and some poking around.

Any advice is appreciated! DIY is preferred but I'd be curious if anyone knows what amount of labor would be involved to diagnose and fix this problem too. Thanks!

[pungo]

You're pressing the unlock button twice, right?
1st time for the driver door, 2nd for the passenger door...