On youtube I found this video describing the tear down of the dock.
Rats, I can't post a link yet. Well, search for 'Asus Eee Pad Transformer Prime Dock Tear Down'
In the comments somebody is describing how to take the hinge apart.
The screws that you can see in the hinge (not the ones under the foam strip) might be worth tinkering with. The outer two seem to be sticking out a bit in my case. In fact they scrape my tablet a bit (two silver scratches just 2 cm outside the slots where the dock connects with the tablet). It might be that they could do with some tightening. Or perhaps by loosening them a bit more the fit gets more tight. I don't know, but worth trying, I think.