Thanks for the report, I'll try to look into it as soon as possible
Viewing post in RPG Maker MZ Plugin: QuestLog comments
I encountered a similar problem when I created the first quest with ID=1. Then I restarted my game. The error appeared!! It seems that the quest ID is not reset when I restart the game. So the previously written quest ID cannot be overwritten with the same ID.
I mean. It happens when I return to the title screen after the quest ID is created and then I start a new game.