Why does the Polyline take some drawing to appear?

Hello! I followed this tutorial and, when executing the second method of line drawing using the polyline, I experience a bug: I have to click and drag for a while and, and then all the lines I’ve drawn will appear all at once, from which point I am able to draw normally.

Nb. I’m on Windows 10 using VS2019 (I make the projects in the Project Generator and have VS2019 convert them from VS2017-format). This and video-playing are the only problems I’ve had so far.

EDIT: In the following tutorial, he uses the polyline inside of the oFB, which works fine for me, so I guess the answer is to just do that.