It’s a known topic. This is the (rather long) main thread:
But you can check the troubleshooting tool of Fairphone as well:
If you select display, it will guide you through a few steps to check first (like disassemble and reassemble display).
If nothing works you will end up on a checkup-page
" Diagnose the issue (insensitive touch function)
If an area of your display is insensitive to touch, please test it with the Checkup tool:
- Go to Settings > Maintenance > Checkup > Free drawing and follow the instructions on the screen.
- Cover as much of the screen surface as necessary to clearly show the faulty area
- Take a screenshot of your drawing (you will need to attach it when creating your support request, in the next step)
If you can see blank areas in your drawing, your display is partly insensitive to touch. "
If this confirms the problem, you are asked to contact support and send in pictures.
Most likely you will need a new display in this case.