Recently, our QA department has been running bug hunts. Once a sprint all the teams do 10 min demos then they spend the whole day submitting bugs for a feature getting ready for release. They've been fairly successful. We find lots of bugs before they hit production, it makes the higher ups really happy to see results, and the winning QA members get lunch.
However, I've noticed a very hostile tone encroaching from the teams themselves. We have 4 scrum teams and the bug hunts have been pitting the QA from each team against each other. This starting to cause a headache for myself and the other QA leads. Testers trying to game the system, complaints about other teams cheating, and generally less than happy office chatter about the hunts. Everyone seems to really enjoy the hunts, but everyone has a reason as to why the other teams found issues shouldn't qualify or they just have general paranoia about what the other team is doing.
Has anyone else had to deal with conflicts arising from bug hunts before and if so, how have you gotten around them?
TL;DR Our scrum teams hunt each others features for bugs. Originally this went well, now QA spends as much time, if not more bickering over validity of found issues. Anyone have an alternative approach?