Ok Maybe I am going mad. I tried again on my MacBook Pro and the same thing. Then I went to the RPI and everything works. The files appear on the RPI and the transfer is a very fast 6 seconds for a 61 mega-pixel image. The only difference, maybe, is I plugged the CEM40G into the USB3 port on the RPI and the camera is, as always, plugged into the USB connector on the declination mount. I can control the CEM40G and read the guide camera which is configured as a V4L2. Also I switched to TeamViewer which is really nice and pretty fast. I only wish I could hide the TeamView control widget.