From your code and all your responses, I think you understand the problem. I don't understand the previous answer 'Actually, the feature for the managing Layout Slides is unavailable'. I don't know how this problem relates to managing Layout Slides.
Anyway, I have done a work-around for that particular problem (by copying the single autoshapeex textframeex info). That has fixed the little problem.
There is still the 'why does cloning drop the box and add bullets' problem. We are trying to clone other slides with more complex pptx pages. I suspect that we will have some of those that will have boxes dropped and bullets added; would be nice to know that won't happen.
Your test code is very similar to what I was doing and did produce the same problem. I actually did the cloning and layout with one call which would be:
in your code, but the result was the same loss of box and addition of bullets.