To reproduce

1. Select a new view-port in model-space
2. Select the appropriate paper-space
3. When the paper space opens change the angle of the viewport to 90 degrees
4. Place view-port in paper space
5. Select the view-port in paper-space by clicking it
6. Try to move the object itself in the view-port (by clicking the "top" dot) to the right by moving the mouse to the right while holding the left mouse-button.

Actual

The object in the viewport moves down vertically NOT to the right

Expected

The object moves to the right

(It seems mouse movement does not compensate for the rotated angle of the viewport)

Workaround

None, except compensate for the angle in your head and moving the mouse the "wrong" way when correcting the placement of objects in the view-port