UR12 sound gets crappy

Hey guys, just got a UR12 with WIN10. No monitors at the moment, so started using it with headphones but sound gets crappy like a high pass filter on and off. Happens almost once in every minute. Comes and goes.

What could be the problem? Thank you

I encountered a similar problem, playing the same piece of audio material repeatedly in cubase, but hearing a different sound each time, as evidenced by inconsistent frequency response (more low frequency/less low frequency/thinner sound/thicker sound.) The UR series is a complete waste of money.