Cyclone-V-SoC: U-Boot fails to fpga load .rbf file - Command 'load' failed: Error -6

Greetings everyone, 

Currently I am experiencing a persistant issue with a QMTech Cyclone V SoC board (a very close clone of Terasic De10-Nano) ,  trying to load the fpga configuration (.rbf) while the board is booting (U-Boot). While the .rbf is being loaded , I get an error :  'Command 'load' failed: Error -6' . 

-Boot SPL 2024.07-36780-g67806ba5853-dirty (May 09 2026 - 16:08:17 +0300)
Trying to boot from MMC1


U-Boot 2024.07-36780-g67806ba5853-dirty (May 09 2026 - 16:08:17 +0300)

CPU:   Altera SoCFPGA Platform
FPGA:  Altera Cyclone V, SE/A6 or SX/C6 or ST/D6, version 0x0
BOOT:  SD/MMC Internal Transceiver (3.0V)
DRAM:  1 GiB
Core:  29 devices, 15 uclasses, devicetree: separate
MMC:   dwmmc0@ff704000: 0
Loading Environment from MMC... Reading from MMC(0)... *** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial
Model: QMTECH C5SOC KFB Dual SDRAM
Net:
Error: ethernet@ff702000 No valid MAC address found.
No ethernet found.

Hit any key to stop autoboot:  0
=>
=>
=>
=>
=>
=> fpga info
Altera Device
Descriptor @ 0x3ffec7a0
Family:         SoC FPGA
Interface type: Fast Passive Parallel (FPP)
Device Size:    4294967295 bytes
Cookie:         0x0 (0)
No Device Function Table.
=>
=> fatls mmc 0:1
  6275664   zImage
            extlinux/
  2082772   soc_system.rbf
    25844   socfpga_cyclone5_kfb_dual_sdram.dtb

3 file(s), 1 dir(s)

=> load mmc 0:1 ${loadaddr} soc_system.rbf;
2082772 bytes read in 111 ms (17.9 MiB/s)
=> fpga load 0 ${loadaddr} $filesize;
Command 'load' failed: Error -6
=>

=>
=> run mmc_boot
switch to partitions #0, OK
mmc0 is current device
...
...

So I would appreciate it greatly, if somebody could navigate me to what to do to overcome this final stage - to get everything working succesfully.

Best Regards,

- Monk M.