We did have a brief Table -> chat with the Director which left us somewhat muted about 'Why?' there was a problem.
He/She simple stated that we needed to "Read".
Other than the "More" description (which BTW clearly had shown UnDo's allowed), I have yet to find any formal link / Help page reference to review.
May not be needed for most regular players, but as a newcomer, we already started a bit lost while just in the Lobby.

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