Thank you for your support of Xiaomi products. This is due to temperature control limiting brightness triggered by the device overheating.
When the device is exposed to strong sunlight, it can heat up quickly. To prevent overheating and protect the hardware, the Xiaomi MIX Flip reduces the screen brightness. This is a built-in safety feature designed to ensure the device operates within safe temperature ranges, thereby preventing potential damage and maintaining performance.
This behavior is a normal part of the device's thermal management system and is not indicative of a malfunction. You can continue to use your Xiaomi MIX Flip with confidence.