A per the title. This is with the default interaction. If the alt key is released before the right button is released the red zoom rectangle stays drawn on the screen and the zoom to region does not occur. The red zoom rectangle will disappear the next time a region starts to draw.

I'm not sure what the best or expected behaviour is here. Possibly one of:

1. As soon as the alt key is released clear the red rectangle and ignore the subsequent right click release?
2. Ignore the alt key release and continue tracking the mouse pointer to draw the red rectangle, zooming to the drawn region once the right click is released?

Either choice makes sense to me. But, since the alt-right click is probably used most commonly with touchpads, I would probably recommend option 2 as it can be hard to hold down the alt key while clicking and dragging with a touchpad.