did you see the help patch “feedback a texture with frame delay”? basically, you need to make a copy of the texture and store it in a pad… the FrameDelay node will only delay the CPU reference, which is still the same reference in the next frame.
you also need to make sure that the copy happens after the usage of the last frame, so that you don’t copy the current frame into the last frame texture.
in general, FrameDelay doesn’t work with references (dashed links) unless it is a new reference for every frame. it only works properly for values and immutable types (solid links).