Perfect shapes/auto shapes not working via Markup in iOS 14.1?

Hey all - I got my new iPhone 12 Pro with iOS 14.1 and one of the first things I did is try drawing a shape (a heart) via photo Markup, and as promised, the shape automatically transformed into a perfect heart.

Fast forward to 2 weeks later, and the function has seemed to stop working? Whenever I draw a shape in Markup (whether through Messages, Mail or Photos), it does not transform anymore. I've tried multiple shapes, all drawn in one stroke, but none work. Similarly, I upgraded to iOS 14.1 on a second device (iPhone 11), but the perfect shapes do not work there either.

Is there a setting I somehow missed or turned off? I feel like I'm missing something really simple here. Any help would be appreciated! Thanks.