I'm sorry about this guys but it seems I overlooked a detail some time ago which caused the current bug with the Halloween event quests. Unfortunately I will be too busy with work to be able to fix this bug in time before the end date of the Halloween event.
This bug will only happen if you are doing both quests from Bubbles and Teddy at the same time, it will not happen if you just do one of them at a time.
To resolve this issue:
Abandon the current Halloween event quests and ONLY do one of them at a time, don't worry when you abandon the quest you don't actually lose anything.