Brightness automatically changes to dim periodically while sleeping-Charge 3

[CMI0929]

I have a new Fitbit Charge 3 that I've been using for almost two months, and there have been a few times that I would wake up and find the brightness level very dim.

After going to settings on the Charge 3, I noticed the brightness level was set on dim. I always have it set on auto, and had to reset it on auto to regain the correct brightness level. 

Is there a reason for the Charge 3 (or any other device) to automatically change brightness levels at any time? 

Moderator edit: added label

Moderator edit: updated subject for clarity

[EdsonFitbit]

Thank you for visiting the Fitbit Community, @CMI0929.

I’m sorry to hear that you are having difficulties with your Fitbit Charge 3.

When the sleep mode setting is on the screen's brightness is set to dim. For more information about this setting, please visit this article.

Have a nice day.