We encounter an issue with the HTML5 Scribble signature. The Scribble signature box keeps moving while trying to sign using a Safari browser on a iPad.
Steps to simulate:
The issue is resolved in the AEM 6.3. Can you please log a support ticket for the earlier version.
Thanks & Regards
Was this issue ever resolved for 6.2? We have same problem. Thank you.
yes. it appears this was fixed in CFP 11 for 6.2. please see the 6.2 CFP release notes at 
Usability issues with scribble component on iOS 10 & 11 devices. NPR- 21092
 Adobe Experience Manager Help | Release Notes: AEM 6.2 Cumulative Fix Pack