I apologize for the delayed response. What model is your iPad? Also, what version of iOS are you using? (Check in System Preferences> General> About...)
Sketch is really optimized for newer devices and recent iOS updates. If you have an older device but have upgraded your iOS, this may be one culprit.
Thanks for your helpful info.
Would it also help to quit the other apps that may be running? Recently, I noticed that the brushes seemed to draw faster in Sketch, if I quit other open apps.
I'm loving Sketch.
Best wishes, Cher