After I had the same issues with my MD600 even after soft powering off several times, after a cold reboot (power disconnected) the problem actually hasn't returned in over a month. Surely good news but I do wonder what did the trick.

Rowland Model6/BPS6, Rowland Coherence II, Levinson 390S and 37, AudioAanZee Reference Flow music server, Rowland Aeris DAC, Rowland Cadence phono stage, Pass Labs Xono phono stage, Yamaha PX-2 and Thorens TD 160MKII, Transparent Ultra and Reference cables, Apogee Diva magnetostatics (refurbished).