I know this is an old thread. But I thought I'd quickly add my 2¢ and mention that my stick (one of the early MCGs) had exactly the same issue.
Of the 2 screws that hold the metal base in place, one had completely fallen out and was rattling around inside the stick. The other was about 1/2 way loose. Needless to say, the metal base wiggled around quite a bit and did not give that tight and precise feeling one would expect of a stick of this calibre.
However, the instructions given by AeroGator in this thread worked very well and the stick is very tight again. One point I might add that wasn't obvious to me at first is that the screws holding the right cover plate you need to remove are on BOTH sides of the stick. At first I just removed the screws on the right hand side of the stick thinking this might be sufficient to take just the right cover off - it is not. You need to take out all the small screws holding both sides of the stick together.
I have not gone out an purchased locking/spring washers and so expect that this may be an issue again in the future. But at least there is a way to fix the problem without having to return the stick for replacement/servicing. It does require a set of very small and long screw drivers so if you don't have those, you'll need to grab some. I got my set for just a few bucks from a dollar store.
FWIW, I was VERY careful not to overtighten any of the screws and did not run into any of the broken screw or cracked plastic mounting problems that others have had - although it sounds like they were being very careful too. So far, so good
Anyway, just wanted to add my feedback for any who might stumble across this thread in future. Cheers.