Need help adding a board_def for flash-sdcard

Hi Folks.

I am trying to add a board or to be more specific three board definitions to the flash-sdcard script since every board revision requires a different filename with no fallback to firmware.bin

While reading the requested filename out of the dumped bootloader hex I made a definition but while testing it it errors out:

mks@mkspi:~/klipper$ ~/klipper/scripts/ /dev/ttyS0 test
mks@mkspi:~/klipper$ ~/klipper/scripts/ /dev/ttyS0 test
Flashing /home/mks/klipper/out/klipper.bin to /dev/ttyS0
Checking FatFS CFFI Build...
Connecting to MCU...Connected
Checking Current MCU Configuration...Done
MCU needs restart: is_config=1, is_shutdown=0
Attempting MCU Reset...Done
Waiting for device to reconnect...Done
Connecting to MCU...Connected
Initializing SD Card and Mounting file system...

SD Card Information:
Version: 2.0
Write Protected: False
Sectors: 245760
manufacturer_id: 0
oem_id: 0
product_name: APPSD
product_revision: 0.0
serial_number: 000005ED
manufacturing_date: 5/2019
capacity: 120.0 MiB
fs_type: FAT16
volume_label: b'SKR PRO'
volume_serial: 2686306684
Uploading Klipper Firmware to SD Card...
SD Card Flash Error: Error Uploading Firmware
Traceback (most recent call last):
  File "/home/mks/klipper/scripts/spi_flash/", line 1373, in sdcard_upload
    with self.fatfs.open_file(fw_path, "wb") as sd_f:
  File "/home/mks/klipper/scripts/spi_flash/", line 337, in open_file
  File "/home/mks/klipper/scripts/spi_flash/", line 430, in open
    % (self.path))
OSError: flash_sdcard: Could not open file 'CHEETAH_V2.bin':

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/mks/klipper/scripts/spi_flash/", line 1647, in main
  File "/home/mks/klipper/scripts/spi_flash/", line 1587, in run
  File "/home/mks/klipper/scripts/spi_flash/", line 1570, in run_reactor_task
  File "/home/mks/klipper/klippy/", line 292, in run
  File "/home/mks/klipper/klippy/", line 340, in _dispatch_loop
    timeout = self._check_timers(eventtime, busy)
  File "/home/mks/klipper/klippy/", line 158, in _check_timers
    t.waketime = waketime = t.callback(eventtime)
  File "/home/mks/klipper/klippy/", line 48, in invoke
    res = self.callback(eventtime)
  File "/home/mks/klipper/scripts/spi_flash/", line 1549, in run_sdcard_upload
    self.firmware_checksum = self.mcu_conn.sdcard_upload()
  File "/home/mks/klipper/scripts/spi_flash/", line 1382, in sdcard_upload
    raise SPIFlashError("Error Uploading Firmware")
SPIFlashError: Error Uploading Firmware

My boards_def looks like this:

    'test': {
        'mcu': "stm32f103xe",
        'spi_bus': "swspi",
        'spi_pins': "PC8,PD2,PC12",
        'cs_pin': "PC11",
        "firmware_path": "CHEETAH_V2.bin",
        "current_firmware_path": "CHEETAH_V2.cur"

I have tested multiple cards - 8/16GB SD-HC, 1GB SD-nonHC and one of my trusty 128MB SKR SD.
On all of those cards the script fails to upload the file while using a sdcard reader on windows works fine and the board updates itself without any hicup.
(Cards were also completely wiped with different linux tools)

I am not a programmer so I am not getting a clue out of those python errors.
Any help really appreciated.

PS: Pic of the filenames in the dumps