Behringer Neutron faulty? Continued...

I have it running ok now, and I have it running from a Model Cycles over midi with headphones. However, the sequence runs fine for a while, then gradually the volume decreases to barely audible. After a while it suddenly goes back up. This seems to happen with any simple sequence I test with. There are no patch leads present.

Does this sound like a hardware issue or am I missing something somewhere?