I watched from a 920 to the 1520. I love the phone so except for this fight I'm having with it and SD cards. I have two SD cards, that are identical... SanDisk 64GB Ultra's. Both are formatted through Windows to exFAT32. With each, if I place apps on them, within a day about a third of then become greyed out and un-accessble. Anyone else having this use issue and/out have a solution? Anyone have a link to a different card of either equal storage size or greater, that they have put through the ringer and have had no problems?