Amax was a lot like this too.....We have all had to swap from the 143s due to this. It was never any consistency and about the time we would think we would have it figured out, we would get one that would be off the charts and fly off. We have had some as bad in 1 box as 138.6 to 149.1 and not have 5 that were they same. Some boxes were better then others but none were worth the time we spent sorting.