Please see the pinned post: About the Vermintide 2 - Bugs Category to see what information to include in your report.
So if you are doing the Chaos Wastes on champion or higher and are running a Greil Knight Bot, after you achieve his the quests buffs, you can kill Kruber yourself and when he respawns he will have his quests refreshed but you still retain the buffs you already earned. The refreshed quest list can roll different quests allowing you to get all 5 buffs. Observe below:
