Timeline skimming while pointer is red or white Using Final Cut Pro X 10.4.5 (Macos Mojave 10.14), I notice that sometimes the timeline pointer is white, then red. With the timeline pointer I mean the point in the timeline where I've clicked, and where a vertical line appears. I don't know the proper name for it. 

Anyway, when this line is white, skimming the timeline works. When it's red, skimming doesn't work. If I click on the film strip, selecting it, then the line goes to white and skimming does work again.

I don't know why the line goes red. I suppose I do something that changes this, but I have no idea what it is.
Make sure you are not have Transform, Crop or Distort icon active under the player. This disables skimming until you deselect it.