This is not an issue caused with the display, rather its an issue by the colour pallete used in dark mode by google and oneplus.
the system darkmode and the google dialer and messages uses a slightly darker shade of grey as the default darkmode colour. So when going under direct sunlight, the phone’s auto brightness sensor max outs the brightness and the grey will be visible.
Its not a display issue.
you can check this by opening this image in gallery and turning the brightness to maximum
Last edited: Jan 26, 2021