Whenever I adjust the brightness it'll flick for a split second what it's supposed to be, then go back to monitor default no matter how bright or dim I make it, sadly it's a little dimmer than I'd like so I'm curious if anyone has a solution for this.

Try solution posted here - https://steamcommunity.com/app/208580/discussions/0/540744937148470760/#c46476690939461530

Doesn't work, my issue isn't that it's flickering non-stop like a bug, my issue is that the brightness refuses to change. Have the bar all the way up, it'll flash what it should be then go back to default. Set it all the way down? it'll flash to pitch black then reset back to default again. The flash only happens once, it's not a flickering, or a returning issue, it's just like the game is saying "Oh you mean this brightness? Nah I like normal better" then changes it for you.

I know your issue is not flickering, but the solution above is not for flickering. The guy who posted it had similar issue like you - brightness setting stuck on default, which was too dark for him.

Alright, I was just making sure for clarity, thank you for the suggestion though however it sadly didn't work :(

I have it in C:\GOG Games
And my monitor uses a DVI-D cable.

Not the solution but I Solved the issue.
I needed to close Flux.exe