The trophy room shows I completed the event but the event won't recognize any further progress no matter how many blocks I exchange.
pixel_player470023931
Because progress depends on all the players in your region.
more info:
https://forum.pixelfederation.com/diggysadventure/d/192855-unlock-rooms-in-the-igloo
https://forum.pixelfederation.com/diggysadventure/d/192859-builder-event-all-you-need-to-know