156 driver's seat - lumbar adjust broken??
 

Hi folks,
I've never tried to adjust the lumbar setting to the driver's seat of
my 156, until today that is....now I wish I hadn't bothered!
Whereas the passenger's seat knob turns quite heavily and can clearly
be seen to be doing some alterations to the seat back, the driver's
side just appeared to spin merilly around doing, well, very little at
all actually.
Everything else on the seat works perfectly, forward / back, electric
back angle, but the lumbar support does nothing.
To make matters worse I gave the knob a yank to see if it would sit in
place better, and the damn thing fell off in my hand. Now, however
far I try to push it back in, it doesn't seem to catch on anything and
just falls off in my hand.
Does anyoine have any experiences of such issues, or am I just missing
something really rather basic here?
All suggestions / solutions appreciated.
Trev