Repro Steps:

1) Create a Page
2) Using the Path Tool (P), place a Path Point on the Stage.
3) Hold the [Shift] key, and move the mouse, to select the position where the next Path Point will be placed.

Observe how the angle of the line snaps to 45° increments.

4) Place the point from Step 3) in any position by clicking on the Stage.
5) Place a third point on the Stage, and then join all of the segments together up to make an enclosed triangle.
6) Using the Path Selection tool [A], select any anchor point, and [Ctrl+Click] on it to convert it to a curve Path Point.
7) Still using the Path Selection Tool [A], grab any of the Path Point Handles, and move it around whilst holding [Shift].

Observe that the Path Point Handles snaps to 45° increments, but is not constrained to those angles.

8) Using the Path Tool (P), start a new Path, and place a Path Point on the Stage.
9) Without deselecting the Path Point created in Step 8), click and hold and drag the mouse anywhere else on the Stage, in any direction whilst holding Shift.

Observe how the angles of the Path Point Handles are this time not constrained to 45° increments.

Expected Results: The [Shift] modifier applies a constrained 45° increment equally to a new Path Point as well as an already-existing one currently being modified.