Yikes. I've had my RR baseplate for some time now, and while there is wear on it, I've never had anything like that happen. How tight were you cranking the screws down!?
My friend has a RR baseplate that has taken some heavy abuse (Student films) but it hasn't done anything like that, might be lemon. Send it back and make them replace it.
The spacer/mounting plate/baseplate was adjusted for one camera over a year ago and never changed. That is, the cap screws were never loosened or tightened since they were set over a year ago. Not once.
All I had on the camera when it detached itself from the baseplate (while mounted to a head) was an FS-100. That's it. No lens adapter or anything. With the baseplate, I've never used more than a non-flip lens adapter, onboard 7" Marshall LCD (on the rods) and the FS-100 (on the camera).
I'm waiting to hear back from RRM, but I bought this baseplate in June '08, so I'm not sure...
Of course, unless the design has changed, I might opt to modify the baseplate I have.