'94 Subaru Legacy-something draining battery

[MariMother]

So recently my '94 Subaru Legacy pooped out on me. Had to get her jumped a couple of times just to get her to the closest mechanic. He tested the battery, which said it needed changed, so we did that.
She ran fine for awhile, then stalled out and needed another jump to get home. (This was on a 60 mile trip) She got home just fine (turned off all accessories, etc.), and didn't idle down once in the driveway. However, once I turned her off she would not start back up.
Took out the alternator and had it tested, surprisingly the alternator was in ship-shape condition. The battery has since maintained a full charge and the alternator is putting out prime power.
However, I've noticed that when the doors are opened (especially the passenger side) it will drop the power point by point, slowly on the meter.

I can supply a ton of other information regarding the incident and what's been checked, if needed.
I'm wondering what could possibly be draining it like that? The seat belts are motorized, but are not in use, could that have something to do with it?
This power issue is a recent development, and all lights (Trunk, dome, etc.) have been checked. I don't think the dashboard display would drain that much power from the battery, so again, I'm wondering if it's the seat belts.

Would anyone have any ideas on what to check/what could be draining that power?

I appreciate any comments/help ahead of time!