Additionally, if I wrap the two calls to make-marray in (cl-array ...) then the test fails correctly and says
(CL-ARRAY (MAKE-MARRAY 'DOUBLE-FLOAT :INITIAL-CONTENTS '(1 2 4))) failed: Expected #(1.0d0 2.0d0 3.0d0) but saw #(1.0d0 2.0d0 4.0d0)
Malcolm