Did you use Remote Displacement on the symmetry planes?  Delete that, it is wrong.

Use Displacement on the symmetry plane. 

For the long center plane, Z = 0 and for the short center plane, X = 0 the others being free.

Use 1/8 symmetry and cut the thickness in half and on that plane, the Displacement BC is Y = 0.

Then you can apply a non-zero displacement along the X axis on the 1/4 end face of the sample.