The remote for our 1997 OBW, the one I carry, got to working very
unreliably, although the one my wife has worked fine. I found out what was
wrong and fixed it, now it works fine.
Inside the case there is a thin piece of plastic, far more complex in its
layout than it needs to be and consequently physically weak, that guides the
push buttons so as to align them over the little switches on the PC board.
That guiding piece was all broken to pieces, presumably because I keep the
remote in my pocket even when rolling over on the concrete garage floor
while working under a car, and other similar abuses it suffers. I milled a
new piece from plastic, much simpler and stronger, and it has worked
perfectly ever since. I realize that not everyone out  there will be in a
position to implement this fix using a milling machine! But the piece has
such a simple function that you could easily make the part from sheet
plastic (I used a scrap I got years ago at TAP Plastics in San Jose, CA, and
have been carrying around the country since then...) using a coping saw,
drill, and files. There needs to be a square recess in one side over each of
the switches, that is what keeps this piece aligned so it in turn can align
the force onto the switch, and that was easier with a mill, but it can be
carved out by hand.
Bob Wilson

My '99 does this. Turns out that mashing on the buttons real hard
breaks the metal battery holder loose from the circuit board on one
side. I re-soldered the holder a couple times, but the kids use the
remote and it breaks again. I ended up adding several layers ot tape to
the back side of the remote to take up the room where the holder was
being forced. It's been going for a couple months again....

-John O

Same with my 01.

To the OP:  

Open up the remote and bend the contacts to hold the battery tighter
and check for corrosion.  It could be an intermittent battery
connection at the root of your problem.   Try the other remote as
well.

--
Todd H.
2001 Legacy Outback Wagon, 2.5L H-4
Chicago, Illinois USA