Make sure you bring along a stack of sickles, as you are likely not to get the Blightberry on the first attempt. You can also fill your main inventory before you start harvesting so that the harvesting point will not expire before you get the Key Item.

I have both quests (Flavors of Our Lives and Raptor Rapture) flagged, and I was able to get the Blightberry no problem. I had not spoken with Gontrain to advance the quest at all before harvesting the Blightberry.

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