Short description:
When buffing a friend on their island, sometimes the game fails to register the buildings that were buffed. Most of the times it just stops registering buffs starting from a certain building. The buffs are substracted from the stackcount initially but will be back when you refresh the game.
Screenshot:
Not available
Possible cause:
Unknown, but having lag does seem to increase occurences.
Prevention:
Buff slowly, wait till the current building is actually glowing before proceeding to the next one
Workaround:
Refresh the game.
Related:
Original thread(s): 1