Posting here as doing a search revealed this is the closest to the problem that I'm having. I've had my AT&T Samsung Galaxy S4 for approximately 1 month now. I purchased a Sandisk 32GB SD Card for the phone. Two days ago I began experiencing issues where when unlocking the phone I would notice the card would unmount then remount (this was in the notification bar). Later that night, the card unmounted and there wasn't any way to get it recognized again. I posted in some other forums and someone said there were some good posts here.
I've contacted Sandisk regarding the card and they refused any involvement stating it's a problem with the phone, not the card. They determined this because once I was able to get the phone to recognize the card and plugged the phone into the PC, the card was able to be read. As long as it's readable, it's fine. After dealing with this I eventually found my MicroSD to SD reader and plugged it into my media reader in my printer. I had quite a few issues from time to time reading the card, however I can't 100% for sure say whether this is the card or the printer.
Anywho, I grabbed copies of what I needed. Formatted the card on the PC, then formatted it on the phone. I began to copy my entries however at one point instead of saying I had 29.* GB Available, it said something like 2.0 EV of 3.0 PE or something like that... these weren't the typical numbers I've seen nor the units of storage space. I apologize that I can't recall that information. I reformatted again and it worked. Left the card in the phone empty over night then tried to copy files later today. This worked.
Now, approximately 48 hours after the problems began, I noticed more issues. SD card stated that it had been damaged and that I should reformat it. While this message stayed in notifications, I confirmed I was still able to read files on the SD card. When googling that error hoping I'd find more resources, the card again unmounted.
One of the resources I found had me do a CHKDSK /F /X on the card. I did this and found no issues. I've replaced it back into the phone and it seems to be working for the moment.
1) Are there any confirmations if this is a bad card, or if perhaps any applications are causing the card to do this? I do have QuickPic and have enabled some of the hidden file features if that helps.
2) Do we know if there are any logs that can be pulled to help verify this?
3) Is it a specific card? (I've heard SanDisk 32gb, but also have heard non-Samsung SD will fail)
Looking to get this resolved ASAP. This card was purchased directly from AT&T when the phone was purchased. I am just looking for some confirmation that if I have to buy another card, I'm not going to gamble if that's going to have the problem as well.
Thanks! If I forgot anything please ask!
Edit: Per the thread, this is a Class 4 card. Also the phone was not moving when it was writing data. I've been couch-ridden all day and unlocked it. I don't believe the phone was in deep-sleep mode as I had received a text not long before I began noticing these messages.