@Saff @kbowman @md673 @Rowananye @MarkBult @Golden28 @hpardy and @gurigurico!
We just pushed a fix for this! You should be able to use the show / hide nav menu interaction on scroll without the iOS elastic scroll causing issues.
Please note this only applies to iOS 9 and above. Any devices with 8 or lower will still experience this issue (we checked and less than 8% of iOS users are on 8 or lower).
Can you please refresh the Designer, republish, and confirm the issue has been resolved?
Thanks in advance!