Object Actions in CP8 are, strangely, on the Format, not on the Actions tab in the Drag&Drop panel. And the opening dialog box has the title 'Accepted Drag Sources' to add to the confusion. Sighing... I thought you were talking about those individual actions that are performed when the corresponding drag source is dragged on that target?
Whow, a lot on that timeline, see nothing wrong but suspect the number of objects could be reduced: do you know that text can be in a shape and an image as well? Did you keep the default pausing point of the D&D which is at 1.5secs as for question slides? Was asking about timeline to see if objects were perhaps invisible after that pausing point.
Planned to blog some time about drag&drop, help is not really sufficient I think, but spent more time lately on shared actions (which are mostly great for individual object actions in D&D).