There is no point in checking the jumpers (actually short wires 1.25" long) because when it fails, it is the card reader, connected or disconnected, that fails. It is the contacts on the card not contacting the case when the card is removed.
PREVIOUS POST (LOST?) REPEATED:
Rick: CD works as you describe - WHEN IT WORKS.
There is always continuity between the metal case and GND whether or not it works.
Inserted and removed card multiple times:
With a card inserted, CD is always disconnected from ground
With the card removed and no connection showing (reader failure), pressing down on one of the fingers DOES connect it.
The first few times I removed the card, CD worked (was grounded).
On subsequent tries, CD worked ONLY SOME OF THE TIME.
(This is, of course, consistent with what we see in our software.)
I find it very interesting that it should fail in spite of the two-finger redundancy!
WHAT IS THE NEXT STEP? Replacing the cards? Voiding the warranty by bending the fingers? (This might be the thing to do to the card reader that is soldered in place.)