I found a post elsewhere from 2012 where somebody was having a very similar problem. The culprit turned out to be Rosetta Stone which was switching a USB Audio Codec from 16 to 8 bit. The fix there was simply to change the setting in Audio MIDI Setup. Unfortunately, that does not work for me because the setting immediately is changed back to 8-bit. This happens only if the codec is in the aggregate device and Cubase is configured to use the aggregate device. I am sure Cubase is switching the setting from 16-bit to 8-bit but I can’t imagine why.