It's not your player's fault.  I am still experimenting with the combo feeds and time synchronization.  When two frequencies are combined on the controller end, and the two individual feeds get out of time sync by even a fraction of a second, echo results.  Trying to work on a way to fix it, but it could take a little while.  In the interim you can listen to either one of the two separate feeds, or perhaps open two players.  This will eventually be fixed.