This video shows you two ways how you can get rid of the flickering editor bug which appears for several users since Engine Version 25 to 26.1
If the first fix doesn't work for you, the second one will definitely do the trick 😉
In case it doesn't leave a comment below and I'll try to help you fixing it.
------------------------
Support my work on Patreon: https://www.patreon.com/ue4mentor