Clear cache in VSE

how do you clear the cache in the VSE.
I have the following setup:

  • one video clip
  • above this video clip there is a scene strip with only a monkey

If I play the timeline in the VSE the whole thing gets written to cache.
Now I change someting in the scene, for example the color of the monkey form white to red.
The cache does not get cleared and still displays the monkey in white.