Can't effectively reveal text with draw mask anymore

I used to be able to reveal text as if it were behind an object in my video clip using a draw mask and keyframing. I followed this tutorial (linked at appropriate timestamp) https://youtu.be/hcmsoWZJdTM?t=195, and it worked well about a year ago when I last did it.

Now, on FCPX 10.4.1, I can no longer draw control points when the mouse passes too close to the title's moveable box. I can drag one point from outside to inside but this isn't a solution. The cursor changes to the move tool when over the box. I made a clip to demonstrate: https://www.youtube.com/watch?v=pP24vBFsAN4

I was really surprised to see this had stopped working. It's really simple so I would've noticed if this were happening last time.

Is there a way to stop the title's box from highlighting when I'm drawing the mask?

Thanks!

Alex