When you use the Assistant Tool, then use a brush to draw without it being snapped to the assistant, then rotate the canvas with 4 or 6, the control box for the drawing assistant becomes non-responsive. The box is visible on the screen, but if you try to use any of the controls to either move it, hide it or delete it, none of those actions happen. Instead it starts a new assistant.

Steps to reproduce:
1. Open a new or old file.
2. Select the Assistant Tool and make a new ruler on the page.
4. Select the Freehand Brush Tool.
3. Unselect "Snap to Assistant."
4. Draw a stroke on the page.
5. Hit the 4 or 6 shortcut to rotate the canvas.
6. Select the Assistant Tool again and try to move or close the ruler you created in step 2.

This only happens when the brush isn't snapped to the assistant. You can draw, rotate the page and move the tool all you want if you're snapped to it. The first time you unsnap and draw, however, then the next rotation will cause the glitch. The only way to remedy the problem is to close the file and reopen it.