How to rotate a plane without flipping it [iTween]

Hi, I am trying to perform a very simple tweening rotation of a plane within my scene. Here are the data points:

 var bin1spin = Vector3(150, 90, 270);
 var bin2spin = Vector3(95, 90, 270);
 var bin3spin = Vector3(40, 90, 270);
 var bin4spin = Vector3(-15, 90, 270);
 var bin0spin = Vector3(292, 90, 270);

the thing is, when I animate from 4 > 3 > 2 everything works perfectly and smoothly, but from 2 > 1, the plane does some kind of 'flip' along the way. It also does the errant flip from 1 > 2 > 3, while it works smoothly and fine from 3 > 4

Please help!!!

here is the trigger code:

 if (Input.GetKey ("1")){
     iTween.RotateTo(binHighlight,{"rotation":bin1spin,"time":.8});
 }
 if (Input.GetKey ("2")){
     iTween.RotateTo(binHighlight,{"rotation":bin2spin,"time":.8});
 }
 if (Input.GetKey ("3")){
     iTween.RotateTo(binHighlight,{"rotation":bin3spin,"time":.8});
 }
 if (Input.GetKey ("4")){
     iTween.RotateTo(binHighlight,{"rotation":bin4spin,"time":.8});
 }
 if (Input.GetKey ("5")){
     iTween.RotateTo(binHighlight,{"rotation":binXspin,"time":.8});
 }