Well John, it's time to share my experience .
(Like you,my pedal went to floor)
You're right ,10.000 km ,it's not much BUT IT WAS NOT THE CAUSE
Stupidly ,i have replaced the slave for a worse one
The deteriorated rim is the rear one ,so not preventing to get the pressure
BUT the rubber débris go everywhere in the circuit ....particularly onto the
little valve situated at the end of the piston'master.
While you're at it ,give it a good clean and replace the fluid...that's all
Mike