Berber has only one defect and it is a good one. They seem not to advise you about this up front. Berber runs like women's stockings and there is nothing that you can do about it. It runs at the slightest case like moving a furniture leg.
You should cut the end of the run and slightly touch it with a very hot knife blade to weld the pull so that it will not continue. Do this on both ends.
Sorry, but find a nice throw rug or small area rug and hide the thing.