Hi, Digital_Igloo. First of all, thanks for your effort in supporting Helix.
My Roland can be used full featured with its driver, or as more simple class compliant unit. I am using as a class compliant.
I am also using a Behringer usb interface, class compliant without any driver, in another mac with El Capitan without any problem.
I think that the bug comes when a program try to send and receive simultaously audio data to Helix, because I've can listen the Helix through USB connection, and starts to corrupt audio when I try to record monitoring the input.