I have a Modern Skyblock 3 3.1.5.3 quest book that got corrupted. My first sign was that I completed a quest, it let me get the reward but it didn't show the prerequisites as being complete. I immediately saved the game, backed up the betterquesting directory, and got back in to the game. When I get in it starts spewing things about new quests being completed and corrupts the quest book. I don't know if it will help tracking this down, but attached is the backed up betterquesting directory.

betterquesting.1.zip