How about some pictures?
That might help remote diagnosis.
I suspect you are going to have to go in and do some surgery, and some pictures will help us kibbitzers give you advice.
What you will have to do is to remove the platter, secure the arm (and, ideally, remove the headshell and counterweight). Make sure nothing is loose, and turn the table upside down on a cloth so that the dustcover is supporting the base (it occurs to me that you should first make sure that the turntable itself can't fall out of the base-- every japanese table I've seen has the baseplate trapped even though sprung, but who knows?
Then figure out what screws need to be removed to take off the bottom. Remove it, and see what the problem is -- if it isn't obvious what you need to do, pictures will really help.