A couple things you might want to check out…
I noticed that the starting frame thingy is not retained in the destination page (the one you paste the content into) - so you have to go in the right side and select it from the drop down or there will be no starting frame. Make sure you click outside the stuff in the page (on the background area) so that setting will appear in that right hand column.
Then also with regard to getting the content into the other page…
I’m not sure if I’m doing it the same as you or not but if I …
- Open the prototype tab (source page)
- Select everything in the page
- Press Ctrl + D (duplicate)
- Press Ctrl + X (cut)
- Move to page I want to put the contents into
- Press Ctrl + V (paste)
That works for me.
Note: I have not tried it with just a portion of a prototype (only the whole thing). Perhaps it would not work if all the links are not selected (ie: some links extending outside the selected part and connecting to other stuff in the page). I don’t really know. But for the entire thing the steps outlined above have been working for me.
Was done in the online Figma (not tried in any desktop app of it)