Damn the pie update, it is the third bug I've found so far. I have a 4k TV and the recommendation resolution it said was 1080p, so I manually changed it to 4k only to found out that mi box would randomly switch it back for unknown reason. This happens too often and annoys me like hell. Fix your bug before you release . , Xiaomi.
Did you disable use recommended resolution or something like that in the settings?