We are experiencing this same problem, I thought we were the only ones! I contacted Panasonic support about this issue several times and the main guy there says the problem is caused by the PCIE bus within the MAC computer. We have moved the reader over to other Mac stations with the same result, its weird sometimes it sees the card and other times it does not, but it always reads it after a restart of the Mac computer. We have even installed a program called jiggler on the Macs to see if this would keep the computer from going to sleep and sending info to that bus, like jiggling a mouse.
And that didnt work, I’m going to email Raj at Panasonic with more info on the subject to see if we can get any more answers from Apple and or Panasonic.