You could try trading these on another platform like Steamtrades or Barter. The Indiegala trade system is not good when you have a suspected bad key, as it exposes both keys simultaneously when a trade is accepted. If you don't have an agreeable replacement for a bad key, then your trade reputation will take a hit. At least on the others you can stipulate that you want your key tried first, and request to cancel the trade if your key turns out to be bad. Of course, you could also do the same thing here using the private chat system.