Fusion Media in Nodes Not Updating with Frame

I have composited a multi-layer EXR sequence from Blender in fusion. I used the 'media in' node extensively. I played around with the cache/optimization/proxy setting a lot to try to get good response time before moving onto color. (I am still learning these terms.) Now the media in nodes in fusion are not updating to a different frame when I change the play-head. They also were all showing the AO pass (first in alphabetical order) regardless of if that layer was selected. I fixed this by changing the layer and changing them back within the media in nodes. Then I realize, when I tried moving the play-head, that the frame being displayed wasn't changing on the media in nodes. What have I done wrong with cache/optimization/proxy? What is the difference between the three terms? How do I fix this?