Instancing a random shape with a random start frame

Here I’m instancing a group of Arnold standin sequences, and giving each instance a different start frame. (Each standin sequence is an animated bulge on a cylinder.)
random shape w random offset
PS It works fine until you go past the last frame of the sequence, because looping or clamping the ShapeInstanceTime doesn’t seem to prevent SItoA from loading the non-existent ass file.