========================================================
The given Problem was:
a b b -> b b a a 
a a -> b 
========================================================
A self-embedding rewrite structure for the given SRS is:
   a b b b b b b --(6)-> b b a b b b b b b (#30)
   OC+OC at 3
      OC: a b b --(1)-> b b a a (#1)
          Rule
      OC: a b b b b --(5)-> b b b b b b (#25)
          OC+OC at 2
             OC: a b b b b --(3)-> b b a b b b (#5)
                 OC+OC at 3
                    OC: a b b --(1)-> b b a a (#1)
                        Rule
                    OC: a b b --(2)-> b b b (#3)
                        OC+OC at 2
                           OC: a b b --(1)-> b b a a (#1)
                               Rule
                           OC: a a --(1)-> b (#2)
                               Rule
             OC: a b b --(2)-> b b b (#3)
                 OC+OC at 2
                    OC: a b b --(1)-> b b a a (#1)
                        Rule
                    OC: a a --(1)-> b (#2)
                        Rule
Hence, the SRS is non-terminating.