I had posted asking about the speed adjustment I broke on a MCP655 pump a while back....no one had anything to offer but I got into it finally. Pulled it apart yesterday and saw that the plastic shaft that engages the component inside for adjusting speed control is super thin and small on the very end. I can see how very little stress on the shaft could easily break it off.
In my case the end of the cross-shaped shaft lodged into the component inside making a "screwdriver" adjustment impossible. I flicked the tiny piece of the shaft out with a hobby knife and now I can reach in with a small phillips or straight screwdriver and adjust the speed.
Here is the shaft with the small piece that broke off, with a pencil for sizing.
My guess is it's intentionally made flimsy so as to avoid damaging the components if accidentally stressed like I apparently did when I put the dress kit/sleeving on.
