Reproduction steps:
1. Open the attached project;
2. Go to the Scene window;
3. Click on the object "Cube";
4. Rotate the object with a button "Rotate X 90";
5. Observe Console window results;

Actual result: the rotation values are shown incorrect in the Console window (1.png) (first rotate - (90.0, 0.0, 0.0), second rotate - (0.0, 180.0, 180.0), third rotate - (270.0, 0.0, 0.0)
Expected result: the rotation values should be shown correct in the Console window (first rotate - (90.0, 0.0, 0.0), second rotate - (180.0, 0.0, 0.0), third rotate - (270.0, 0.0, 0.0)

Reproduced with: 5.3.6p4, 5.4.3f1, 5.5.0f3, 5.6.0b4

Note: the rotation values of x axis are shown correct in the Inspector window. The wrong values are shown just in Console window.