I seem to have run into a problem in the last couple of weeks where whenever I change my buffer Cubase stops playing any sound and the only thing I can do to get it back is change the buffer back to what it was. In order to actually get a different buffer size to work I need to change the buffer size then restart my computer. It’s getting very annoying.
you are opening the driver through Device Setup/ ?
I have experienced similar problems with both Motu and TC devices, got fixed in both cases with a driver update.
RME usually are pretty good at drivers. Are you syncing you babyface to external clock ?
You could try disabling any wdm channels you may have set in the RME driver.