I have a Snapdragon 888 version of the S21FE which I find is a great phone overall. But two issues are bugging me. Firstly, is screen dimming issue. I have auto brightness turned off and any battery power saving modes are all turned off. Screen is set to Vivid but when I go into certain apps like Facebook Messenger and Maps among a few others, the screen just keeps dimming. I've tried absolutely everything but it still dims even when I'm outside in bright light. Software is upto date and when I got the phone I reset it before setting up. Also whenever I have my charger plugged in the whole UI slows to a crawl after about 10 minutes. Phone isn't hot or even warm for that matter. Apart from these two issues it's a great phone. Does anyone have any answers for these issues??
Unfortunately I'm not using your model of phone @Shamrock_Sean so I may not be able to re create the issues you speak of.
I wonder if it's possible that the screen is dimming when in Maps for a length of time to stop screen burn/ battery depletion.
Does the same happen when your display is set to natural mode ?
I would suggest to throughly check the apps preference settings and if necessary contact Samsung via your Samsung Members App to give feedback and perhaps the app developers too. ( Can't hurt to do so ! )
When a phone is on charge it's possible the phone may react differently due to it's status of charging. I've read similar posts before where this has been the case.
A Samsung Service Centre can help you by looking at the phone.
I wish you all the best.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I have no affiliation with Samsung.