As I mentioned in a previous post I had my Dremel 3000 for about 3 years but in that time it had probably only had about 30 minutes use if that. This time it was a problem with the Shaft Lock, the button you press to stop the shaft turning so that you can remove or unlock the Collet/Chuck attachment. When I pressed the blue button the lock would slip as soon as I applied any turning force to slacken the Chuck/Collet.
Dismantling the Dremel, no difficult if you have done it once before. See my previous post for a link to the teardown or click here to see a YouTube video showing how to dismantle the Dremel 3000 and replace the Shaft Locking Pin. Please note the video refers to removing the screws that hold the body together but it does not mention that they are "Torx "screws.
I ordered the replacement parts on eBay from here.