Fastboot -w/erase likely corrupts the partition table on the innerSD,
seeing as it was prob due to dell never updating their fastboot loader to take it into account. (The Venue doesnt have this issue as it doesnt have an innerSD).
You can fix it by either restoring it to a known good image (there's a thread on the main subforum) or by manually repartitioning your innerSD.
You will need to disassemble your S5 to do it (regardless of who does it) and a pc with a SD/microSD port then just reimage it, it's not very difficult besides the disassembling part.
The firmwares are on the nand, but we cant read to it, and the only way to (safely) write to it is the stock rec.
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Nexus 4: Stock JDQ39 (4.2.2) Nexus 7 Sucessor: Waiting for it
iTouch 5G: Stock 10B146 (6.1.2) Venue Pro: Stock 219-33 (7.10.8862.144)