We are pleased to announce that the handwriting lag and stuttering issues in the app have been identified & fixed by our developers in version 4.5 (171). Thanks for your support & patience with us.
Please update your app to experience the most fluid handwriting experience ever!
We're working on further optimizing this fix for Matepad Pro & S6 lite devices. Feel free to write to us & provide us with your valuable feedback via Gear icon->Support within the app.