Unfortunately, this often happens, and it usually always depends not from the bounty manager, but from the company that doing the bounty, because specifically in each bounty the rules are written that at any time the company that doing the bounty can change the rules and reduce the bounty pool, and with this of course, its very difficult to do something, but there is always a way out in such situations, namely, all bounty hunters need to get together and fight with the team of such companies.
How would they do that when you know that everything we do is over the internet and to get people coordinated over the internet is something that is very bad, and the only way that I feel we can just stop all these abuse by these team and developers is to stop participating in some of those projects that cannot attest to the credibility of the developer or the project team, because many credible developer or project team would never cheat or do all those sort of rubbish at the end of the campaign.
Most of those projects that do that are either scam projects or they end up being a bad project because if they cannot manage ordinary bounty campaign, how can they manage the whole project? So, I am not sure we can fight them but we can at least make little impression.