Does your cursor jump from the “Address Bar” to the Body of the message when composing an email?
After weeks of searching the internet to find nothing but others having the same issue here is the solution:
Check to see if your running Sophos “Hit Man Pro” http://www.hitmanpro.com
Under Safe Browsing / Disable “keystroke encryption”, appears to be a bug that the developer has yet to resolve as of May 2018
Curated by Hostcheetah, Sponsored by Liquid Layer Networks
http://www.liquidlayer.net