Drag scroll not working as expected in spectate-mode

"Mouse button drag scroll" was implemented in the game about a year ago I think. This is working perfectly. However, when using the same feature when spectating a game, the drag-scroll behaves differently. Instead of grabbing the map, it 'teleports' the camera to the position where the user 'grabbed'. Granted, it works like a drag-scroll after that 'teleport', but when you let go; the cursor appears at the same position as where you started grabbing. The cursor should move with the drag-scroll.

Step 1: Enable "Mouse button drag scroll" in Options->Game Step 2: Press middle mouse button (scroll-button) and 'pan' around. Step 3: Do step 2 in-game and in-spectate. Notice the difference. In-game is working correct.