When I bought my TV, It was always in 120 hz mode, when I was gaming on my Nintendo Switch, but, at some point, I had to factory reset It, and since then, It no longer does.
About two months ago, I was screen mirroring my Apple Air and suddenly It increased both brightness and FPS, but when I had to turn off my TV and turn It on in the next day, It went back to 60 fps. I've already asked my local tech support, but they couldn't help.
Thank you so much for reaching out! This forum is for the support of US products and customers. We do not have the ability to support models outside of the US. There are differences between the US and International firmware, which we do not have access to. Since your product was purchased outside of the US, please visit the link below for support in your area. https://www.samsung.com/us/common/visitlocationsite.html
