I agree with the switching. I've stayed at CBR twice. One time I got my request (which was just for Aruba in general --- and we got the furthest one out there, but was a waterview, which we paid for). 2nd time, I did not get my request at all (which was for the ever popular specific Jamaica/Aruba bldg.) and even then, she would have to go over the bridge, so a little walk. Anyway, we ended way up on the parking lot side of Barbados (which was fine for us, and by the way, the bus was right at our back door, so that was a plus). When I asked if they had anything for our room request, it was a no way. We had also checked in bright and early.
You may want to take a different approach if you are set on staying at CBR. Since everyone requests those Jamaica/Aruba bldgs., try requesting the next closest buildings that are not preferred. When the Barbados buildings start (just look at the map), pick the building closest to Martinique to request. That building will be just about as close as a preferred to the OPR and also will be near the Martinique bus stop. Not as many people will request it probably either since they all want those other two buildings, and therefore their may be more availability to it.
The way it was explained to me when we went, was that people checked in like the days before us, and everyone requests those two buildings, so now they are in there for a week, so they are not available.