Sony PMW-RX50 Operating Instructions Manual page 64

1)
If recording/playback cannot be made with an SxS
memory card because it has been operated with a
device other than this recorder, or for some other
reason, updating the managerial file on the card may
improve the situation.
64 Setup Menu List
2)
When you copy an SxS memory card including
multiple clips and files to another card with the same
capacity, all the clips and files may not be copied
completely to the end, depending on the usage
conditions or memory properties.