There seems to be a bug when copying and pasting nested objects (or at least nested frames & containers).
On board 1, all frames are contained, so if I drag the outer frame everything inside moves with it.
When copying and pasting onto another board, the nesting is lost for many of the frames. They appear behind the container and are no longer inside it.
Screenshot:

(In the bottom one, all the light gray objects are hidden behind the frames that they were supposed to be inside of.)