On my 6V '65, when I press in the clutch (via the pedal) with the engine
OFF, it works fine... no weirdness or anything.
Start the motor and as I depress the clutch it starts to whirr - then there
is a "clunk" followed by normal clutch action.  Sometimes it was FAR TIGHTER
than it should be, and even when shifting between gears there was chatter -
but often depressing it would loosen it to where it should have been with
normal function..... after there is a clunking noise.  Have been running the
same clutch/pressure plate for about 6 or so years - daily driver, but not
as many days this past year... got to telecommute quite a bit.

 It started when I made a quick turn out of a parking lot into a road and
the surface was a little damp and there were some pebbles, so the back end
sort of powered around the corner with a little bit of additional slipage.

Replaced the front tranny brace a few years ago, but it looks at least like
the central rubber is split up the middle.

The pressure plate I have has the central ring and a couple of "arms"
reaching up from the edge to support the throw out bearings (with springs
keeping the pressure on.)