Brightness doesn’t increase past 50%

Hi,

I’m having an issue where I cannot seem to increase my display brightness past around 50% on my iPhone 13 Pro Max.

When I manually use the brightness slider I can see it doesn’t improve brightness at all once it’s past 50%.

I have tried turning off auto-brightness, True Tone, reduce white point, zoom filter etc. None of these methods have changed anything.

I have tried the old trick of turning the phone off and on. This solves the problem for about 20 seconds after turning on, but then fades back down to 50% again (even though it still shows as full brightness on the slider).

I haven’t tried resetting anything on my phone yet, as I would always rather avoid the hassle of doing so. Can anyone recommend an alternative solution before I resort to the resetting process?

Thanks