Yes! This happened to me, and I think it might have damaged a channel on my DT50.
I recently bought this amp, and have it paired only with the POD HD500X. Suddenly, Channel B has lost its 'oomph'. Identical knob/topology settings b/w Ch.A & B yields a pronounced difference in volume and low end, with B sounding 'tinny'. This is universal, guitar direct or Line6 Link. Tube problem? Other?