Hey James, I'm a new member myself... long time lurker haha
I may or may not have THE right answer for you, as I'm unfamiliar with your weather station. But, in my experience with Davis and Kestrel weather stations, you have the ability to set elevation. Because barometric pressure is factor of elevation, changing the value of the elevation at your site will result in a completely different pressure reading. Does your weather system ask for elevation by chance? If so, this would probably fix the problem. A few feet won't make a significant difference however so a close approximation should work just fine. But if not, if there's no prompt for elevation, then I really have no idea what would be causing the low pressure reading.
Things like exact station placement, sun vs shade, on fence/on ground, etc., should not have an impact on your barometer reading like it would with a temperatures/wind/rain/RH sensor.
What I DO know is that barometric pressure typically changes very gradually over distance; short of, say, a cold front - or some sort of weather system with a steep pressure gradient in your vicinity - your barometric pressure should be virtually the same as your local weather ob.
John