You may have a bad card socket on the Rumba. There's also the issue that the timing is not quite the same on all of these interface boards. A marginal SPI implementation on a card may work on one and fail on another one. SPI i/o is not a big priority for these guys. I've had cards come in one day that all work (50 of them) and the ones that come in the next day don't work at all (all 200 of them). Both batches of cards appear to be identical / same brand / same model / same size / same interface trying to read them / same same same ...
All 250 cards work fine on any number of PC's. They all work fine on three other boxes (slightly different interface). There's one machine that likes the batch of 200 better than the batch of 50.
All 250 cards work fine on any number of PC's. They all work fine on three other boxes (slightly different interface). There's one machine that likes the batch of 200 better than the batch of 50.