Microchips do not migrate, they are injected into the nuchal ligament where tissue grows over them preventing them from migrating.
As for the restof your post, Have you got irrefutable evidence of this and can we see this anywhere other than on your various pages which in all honesty is your own...
Doing some research on the number of Herds on Exmoor, why is it that, according to the TV coverage, only two Herds of the 21 have this problem. Is it because of mismanagement by these two Herds, ie: not getting all there stock DNAd before the stud book closed, then along comes a saviour who...