Help with continuing touchscreen issues - iPhone 6 - iOS 11+

Since updating, my iPhone has intermittent touchscreen issues. Mostly on the left side of screen, when scrolling on web or in apps, touch response is non existant. Also happens in calculator app. Brought phone to Genius Bar, they did hardware tests, everything checked out. Issue continued so I worked with Apple support to perform complete restore. It is still still happening...

Quite disappointed given level of effort put into resolving issue. Anyone else having this intermittent issue ? Anyone know if this is purely a software issue?

Thanks.