Bob: It really sounds like the brakes are out of adjustment. Had mine adjusted this past fall (early) and went from 6.8 on my prodigy to less than 5 (4.6 / 4.8). Now, after traveling to Albuquerque, Waco, and a couple of other places, it is back to the 6.5 range. As the brakes wear, i.e. have further to travel to make contact with the drums, the magnets take more juice to push (or pull -- I never can remember which way they actually move) the leading shoe out.
As for the distance you take to stop, I don't think you have a frayed / shorted wire as, from what I've read, the prodigy is very good at providing error signals if there is an open short anywhere. A fully broken wire might exist, hence that brake would not be working at all. I don't think the prodigy detects that and you'd definitely take longer to stop on 2 or 3 brakes than all 4.
On my mountaineer I can take it to a loose sand or gravel road, and it will slide all 4 tires using the hand slide on the prodigy at a little over 6.5. (I was taught to take it to where it did that, and then back off .5 or so as an initial point of reference. Has worked for me so far).
Once again, I'm verbose. Sorry!! What can I say, I enjoy teaching and talking, hopefully doing the first when doing the later
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