Any updates?
There isn't any reason why other birds would lock, but AMC1 will not if the skew was properly set.
Did you adjust the LNBF skew specifically for AMC1. As LAK7 pointed out, AMC1 skew adjustment is quit different that the neighboring birds.
I still believe that this issue is install related.
We would love to hear what your installers said when you told them that the dish had been aimed at the wrong bird......