MAYBE
Trs:
 {   c(f(c(a(), y, a())), x, z) -> f(b(b(z, z), f(b(y, b(x, a()))))),
     b(a(), b(c(z, x, y), a())) -> b(b(z, c(y, z, a())), x),
  f(c(a(), b(b(z, a()), y), x)) -> f(c(x, b(z, x), y))}
 Comment:
  We consider a duplicating trs.
  FAIL:
   Open