This is a problem with the separator of UITableView in applications, which not support iPhone 6/6 Plus resolution.
You have an application which works well on iPhone <= 5s. But on iPhone 6 or 6 Plus (device or simulator), the separators have a different thickness, and they change the thickness randomly when you scrolling the table as the screenshot:
The problem is that your app doesn’t support native resolution for the iPhone 6 and iPhone 6 Plus. Therefore it gets scaled up which results in the flickering.
Open you .plist file and add this key & value
Renders with edge antialiasing: YES