ads-b update

I looked at the FAA report for two other pilots that flew out of the Williams area on Friday 4/16, Ramy ( https://www.dropbox.com/s/f7wgkinoru...55266.pdf?dl=0 ) and Peter Deane ( https://www.dropbox.com/s/8vkprmv4gu...57927.pdf?dl=0 ). They both had pretty identical long flights all the way around the top of the valley to Trinity Center and back down the Eastern edge of the valley, then back to Williams. Ramy showed a normal report, while Peter showed 48.01% fail on Baro., and 48.01% on GPS. alt. Why are these two 48.01% numbers identical? Bad ground station for part of the flight? If so why did Ramy have no issues with Baro. or GPS Alt.?

Matt