Down arrow key not working properly while using voice over on Mac 10.12.6 Safari 10.1.2

After current Safari version upgrade to 10.1.2 from 10.1.1 the down arrow key stopped working properly when used along with voice over. While reading screen content using down arrow key it skips reading some content. But before the upgrade, it was working fine. So any idea what changes took place in this safari version upgrade such that voice over skips reading screen content when the user reads the content using down arrow key.