I have exactly the same problem. It’s very annoying on large projects. I didn’t have any problems with this in 6.5 so is it really a Yamaha bug or a Cubase bug?
It’s bad enough having to re-install the DM200 as a device after every shut down, again this wasn’t an issue in 6.5.
Also the channel names disappear in the mixer view in Cubase and can only be rest by enabling ‘pictures’ in the mixer view.
I’m fairly disappointed with 7 to be honest.