Amazingly, I managed to translate the Polish (thank you Google)! Animate now uses a separate process to smooth your brush strokes.
Yes, that's a known issue that I below has been fixed already, and hopefully will be in the next update. I'm not sure when the next update will be released.
Another problem was fixed too, that would happen with FLAs that had H.264 video embedded, which it looks like you may be doing. Don't know for sure if the two issues are related, but one thing you could do is import the images of the frames you want to trace, and use those instead of the original video.