It is usually happens because some bounty hunter sales their token immediately no matter the price is , that is why the market dumped automatically.
The team don't give damn about the bounty hunters and their affords. I think it is right idea to sell the bounty rewards for the making profit after the news about getting listed on the exchanges.
Why immediately sell the coins of the project which you are advertising? After all, surely before you participate in the bounty, you are studying the project and understand its prospects? If you are doing like this then it is better to hold tokens and not to sell