Two years in regular service and the only issue I've had with the CM5 is that the pins of the large brush wheel don't fit quite right, so sometimes the wheel doesn't spin. I've never had an issue with the quality of the cleaning job.

I use two applications of full strength Simplegreen, running the chain about 90-120 seconds on each. Then once or twice with water to flush it. If you have stuff that is still stuck between the links, seems like it could be dried on. Maybe try one application of SG, and let it sit for a few minutes, then go again.

Once every ~250mi and my chain still goes from black to almost new shiny. Use a separate brush to get the chainrings and cogs, then dry with a reverse vacuum cleaner and your drive train will look like something special.

BTW are you guys filling the CM5 to the fill line?