This is in regard to research cards from the 4th chest:
Spoiler (click to reveal)
Specifically the Treasure Maps. Did you ever run into players acquiring half of a map, but then never use the card for it's research ability to save it until they get the other half, but other players doing the same so that most of the maps are in play, but split among different players and thus never ever getting to be used for the treasure map? Seems like this leads to a permanent stalemate as there is no way to raid a player for maps/research or force the discard or use of hoarded cards. Right now in our game (9 games) I'd say 90% of the research deck is in the hands of players.
Also, was there any balance issues if any one player acquires and completes multiple (or even all) the maps themselves vs those who completed none?