Actually the dispute is not handled by the author himself, it is handled by the Youtube and Content ID aggregator (AdRev or similar) and their reaction time can vary a bit, that is true. The reason why you can get things happening faster via contacting the author is because author can mail AdRev and ask for the release of the claim and that can work as a “speed line”, but it is not the system that is meant to be used.
Regarding the other matter, that usually means that either the second claim is erroneous (which you can dispute in any case with your licence) or the tune itself you have bought from AJ is pirate copy (in which case you should contact Envato and handle the situation with them).
To be honest, if you are paying for the music only a handful of dollars, Content ID system is really small pain for that cheap price. You should be willing to pay hundreds of dollars for music if you don’t want to accept any kind of copy protection.