I suffered the same problem early on with my Roadster when the post snapped off flush with the panel. It’s a woodscrew fastening. Later cars have a pop fastener there. I have a modellers pin chuck in my toolkit which is a hand held manual drill holder, and I drilled down the centre of the screw – it took ages but I daren’t use an electric drill in case it slipped. Then I tapped in a triangular profile needle file, just far enough to get a grip and it wound out, it’s not tight.
You might be bold enough to attempt a Dremel on slow speed, but if you do that, stick a penny washer over the hole with double sided tape so the drill can’t slip.
Good Luck.
