strange bootloader/ boot-loop problem on g800f

Hi,

I have a Samsung Galaxy S5 Mini G800F (stock rom, no custom recovery, no root). From one day to another it stopped working and hangs in a boot
loop now. After displaying the samsung logo it shows green rows for a few seconds and restarts. It is possible to go into download
mode with home + volume down + power on, but not in recovery mode with home + volume up + power.

What I have tried:

• reflashed stock ROM from sammobile.com with odin 3.10.6 without errors, problem still exists


• reflashed stock ROM with odin flags "re-partition", "Nand Erase All" and corresponding PIT file without errors, problem still exists


• flashed TWRP 2.8.7.0 but couldn't enter recovery mode


• rooted the device with odin, same behaviour


• adb could not find device

What I can exclude:

• display is ok (no flickering or pixel rows in download mode)


• battery is ok (works with other smartphones)


• power button works properly (phone does not start while inserting battery)

I think the problem lies in the bootloader. Is it possible to re-flash the bootloader and if yes, how is it done?
Is there anything I can do or is the phone hard-bricked now?

Thanks for your help! :good: