Whilst working on a bug in the C&C Napoleonics v3.42 module, I realised that there was what I am pretty sure is an undo bug affecting decks.
In this module, there are two player hands (private windows). Each window has two multi-action buttons defined that perform the following-
Selects all cards matching the specific marker type (e.g. "Command")
Discards the selected cards to an empty deck that is offset from the board (hence, hidden)
The deck is "always shuffle" and "draw face-down".
A card is drawn from this pile and sent to the main board, where is appears masked but the owning player can see it / flip it.
Finally, all remaining cards in the temporary deck are returned to the player's hand.
There is a bug in this function, in that the returned cards are also masked (they should all be flipped up). That is not the problem, however.
The case is:
1) Press one of the multi-action buttons
2) UnDo
3) The affected cards will now be back in the player's hand but all are masked as if no longer owned by the player e.g. can no long be flipped.
I have developed a fix to the module bug that results in flip-down on return to the player hand in normal operation but the undo bug persists. As part of this fix, I created an action button that flips all cards in hand by performing the same action as the afore-mentioned buttons apart from the random draw to board. This results in all cards being turned face up, including the masked cards from the Vassal undo bug.
Deck UnDo bug - Example for CCN module v3.42