Resolution drop when playing footage

I know I ticked some box that I cannot remember to uncheck, but my resolution drops only when I press the spacebar and play footage on the timeline. However there's no cache, no timeline proxy mode. What do I have to turn off?

Though you said that there is no Timeline Proxy Mode set, are you sure? That behaviour is what I would expect to see if one is set.

Hey Charles, thanks for getting back to me! I'm 100% sure.

Take a look at Preferences -> User -> Playback Settings -> Performance Mode

Take a look at Preferences -> User -> Playback Settings -> Performance Mode

This.