I did a Full Reset last night on my 640 to try to correct some issues with accounts in W10m, while those were fixed, a new issue with Storage came up. "Phone" is no longer listed in the Storage app and the name of the SD card is garbled characters, something different each time I open the app actually. Also, the dropdowns to choose which storage device to use for downloads, apps, etc. have no options in them. Everything appears to be saving to my SD card though.