Messing around with the canvas timeline, our collision detection isn't quite right. It's definitely the dotMargin.
Created attachment 375315 [details]
This patch 'fixes' the problem, but it's definitely the wrong way to do it. It feels like the actual x value of the dots is wrong.
Created attachment 375321 [details]
Comment on attachment 375321 [details]
Clearing flags on attachment: 375321
Committed r248117: <https://trac.webkit.org/changeset/248117>
All reviewed patches have been landed. Closing bug.