[Galaxy S 5 Q&A, Help & Troubleshooting] ryannathans:
Hi all

Came across a Samsung Galaxy S5 I've now taken the liberty of trying to get working...

The phone was purchased from eBay I believe - brand new and in original packaging. The instruction manual is Japanese, as is parts of the ROM so I'm assuming Japanese origin.

The model number in the phone settings is quoted as SM-G900F, under the back case of the phone the model is quoted as SM-G900J, on the box and at places in the ROM it's quoted as SCL23. Which is it??

User has never modified the phone firmware/recovery or flashed the device. The device has knox 0x01 and a custom ROM on it which perhaps the seller installed?

All the following problems started around mid day yesterday, user was not doing anything unusual with the device - just regular usage.

The problem

Wake lock started mid-day yesterday according to the graph in settings. Continues after phone restart

At the same time, sending and receiving text messages became extremely slow/delayed. The phone just shows the spinning icon next to any text that is being sent (same in Hangouts and Messages) and the text takes 10 minutes to a few hours to come up on another device. Sending texts to the phone is also just as slow. (phone calls work fine)

Mobile data is working without issue

Google Play store does not load - eventually shows that the login is not valid after a long wait

Snapchat does not load correctly

All other apps appear to be functioning

All files in private mode have been lost, adding files to private mode seems to delete them when private mode is disabled (nothing shows up once the mode is enabled again)

Unable to install APK files locally, after clicking on the APK nothing comes up

Phone no longer shows up on PC as a media device or filesystem. Computer does recognize the phone in device manager - although I think it's coming up as something other than what it normally comes up as

"Reset to factory" accessed from inside the phone's settings does nothing when the button "delete all" is pressed

Samsung "smart switch" PC software sits on "connecting to device...." until it times out.

Samsung "smart switch" emergency recovery/initialization options ask for model number and serial number - only IMEI and model is printed on the box. Under the battery there is only IMEI. Inside back case on phone it says only the model. In the settings of the device it has a serial number listed which is around 8ish characters in similar form to 123456a78. None of these numbers are accepted by smart switch as the serial number. (device is not even plugged in to PC, why do they need the serial/model?)

What I've tried

Booting in to recovery - there doesn't appear to be a recovery. Holding the usual button combination brings me to a single screen with a long paragraph in Japanese and a yellow escalation mark with two options. Pressing up volume key restarts the device and the down volume key enters download mode/ODIN

Smart switch software on PC

Resetting the device to factory settings - a bit difficult with no working recovery and the option in the phone settings not working

Found a recovery/root to flash that promised a stock recovery and root (I really just wanted a stock recovery or A recovery) on these forums, flashed via ODIN and device restarts immediately to ODIN saying "device could not boot" in red at the top. Turning device on every time resulting in this "could not boot" - still the same screen shown when recovery buttons are held

Flashed a recovery (looks successful on PC and in ODIN on phone screen) not CWM, the other starting with a T whose name eludes me right now - phone boots up normally in to the buggy system immediately after flashing but doesn't usually boot up when restarted or turned on normally. Still the same screen shown when trying to boot in to recovery

In about 12 hours, if nobody suggests anything else, I plan to flash a stock ROM or cyannogen mod in the hopes that this fixes whatever issue is happening here.

Any ideas?

Thanks in advance!