I always wondered how a bead could get lodged in a valve if you were adding air:dontknow: Deflating possibly but if you position the valve anywhere but the 6 o/clock spot even then a quick blast of air should clear it.
It's been many years, but I'm positive the valve stem was at about 3 o'clock with the left happy trails pannier removed for access. I checked the air pressure after the tires had cooled down, and could not get the valve to seat with the little portable compressor we brought with us. If I had access to a large compressor with higher pressure/volume it may have resolved the issue.