artifact in stratagene lambda zap libraries

Recently I've screened two different rat libraries from Stratagene, a
brainstem/spinal cord and an adult whole brain.  After sequencing several
different clones, I realized that all of my clones have the same 8
nucleotides after the RI site, GGCACGAG, and then the clones are
different.  Is this a artifact of attaching the RI linkers?

Please e-mail responses to "ting at cmgm.stanford.edu"