Whenever I watch a Youtube clip, I have to wiggle my mouse every minute because I have "dim screen after 60s of inactivity" enabled. In the pre-1.0 version, there was a toggle to override that setting
That's not a bug, just disable the "reduce brightness on inactivity" feature.
Actually I think it's the Presentation mode that fixes this bug. I can't remember now, but I think it was removed when switching to 1.0