Exact same issue here on:
New M:S, firmware 1.12
Cubase Pro 10
Macbook Pro (mid 2012)
OSX Sierra
Elektron’s own USB cable going straight into the Macbook Pro.
When attempting to use the M:S as audio interface for Cubase it drops our after 2-3 minutes and I have to either restart the M:S or pick another audiointerface within Cubase and then pick the M:S again. It then works for a couple of minutes before dropping out again. I also seem to have latency problems when streaming audio directly from the M:S to the DAW through USB. Disappointing.